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Hi all, (please note supporting pictures for the below at? /g/TekScopes2/album?id=278771) I am starting work on this SG502, so its condition is virtually unknown, but during the visual inspection, I noticed the right leg (as per picture) of C160 is detached. Measuring it returns pretty high (over 450uF) and a good amount of ESR, so this being in signal path, I decided to replace it with a high quality, low-ESR cap. More on that specifically at #2 below.? A couple of issue with that.
- To access the trace side of this (namely the pads to unsolder this cap), I need to remove the long fingers of the MULTIPLIER switches (see pics). Can anyone please remind me (I have a feeling I did this before but can't think of how I did it) how to take apart those switches? Namely, remove the extending part so I can properly solder a cap there.?
- The cap itself has markings indicating it may be a tantalum, but is that really so? A 350uF/15V value seems really high for that, and aside from that, it rather looks like a bipolar electrolytic. Thoughts on a correct replacement?
Thank you, Radu.?
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From memory of that far back.
Those Tantalex caps, I believe are "Wet" tantalum types. Personally, I've not known one to fail, unless grossly over-voltaged!? But there is always a first time.
The black extenders to the push switches can usually be gently persuaded off the switches themselves with a little persuasion from a flat screwdriver blade to spread the gap in the black part, then pulling away from the switch.? Be gentle, at their age, the black plastic might have become brittle.
"Have Fun"...
??? Dave ex Tek UK of that era.
--
Created on and sent from a Unix like PC running and using free and open source software:
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C160 is Sprague type 113D which listed as high stability, low leakage tantalex foil 85¡ãC tolerance +30/-15%. ?
Likely a timing circuit premium component. ?I would reattach it, ?debug all other issues and attempt calibration before considering replacement.?
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It should also be noted that if it is a timing cap tek sold the timing caps as a set, ratio stability is importent here not absolute value. Should NOT be replaced unless proven beyond a doubt bad. Timing service was also not a high stress application so in this case ESR is not a critical spec.
On Sun, Sep 25, 2022, 1:04 PM benx618(g) < benx618@...> wrote: C160 is Sprague type 113D which listed as high stability, low leakage tantalex foil 85¡ãC tolerance +30/-15%. ?
Likely a timing circuit premium component.? I would reattach it, ?debug all other issues and attempt calibration before considering replacement.?
|
what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
|
Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...).
After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.?
Thank you all for your input! Radu.?
On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin < jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
|
Hi all, Does anyone have information on the correct power lamp for this unit? I can't find that info - all I can find in the manual is it being a "DS346." Thank you, Radu.?
On Sun, Sep 25, 2022 at 10:12 PM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...).
After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.?
Thank you all for your input! Radu.?
On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin < jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
|
I LEDed mine when it went out. If I remember correctly, I used a fairly high current limiting resister because the LED was so bright it needed to be cut back quite a bit. ? Glad to hear everything is working. The SG502 is a wonderful unit to have in the lab. ? Zen ?
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Show quoted text
From: [email protected] < [email protected]> On Behalf Of Radu Bogdan Dicher Sent: Monday, September 26, 2022 9:28 AM To: [email protected]Subject: Re: [TekScopes2] SG502 Repair ? Hi all, Does anyone have information on the correct power lamp for this unit? I can't find that info - all I can find in the manual is it being a "DS346." ? On Sun, Sep 25, 2022 at 10:12 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. ? I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...). After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.? Thank you all for your input! ? On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin <jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
|
Does it look like this?
Glenn
On 9/26/2022 9:28 AM, Radu Bogdan
Dicher wrote:
Hi all,
Does anyone have information on the correct power lamp for
this unit? I can't find that info - all I can find in the
manual is it being a "DS346."
Thank you,
Radu.?
On Sun, Sep 25, 2022 at 10:12
PM Radu Bogdan Dicher via <vondicher= [email protected]>
wrote:
Well, I had no symptoms yet to?file, as until
tonight I didn't get a chance to even plug it in. Visually,
the only?clear issue I was seeing prior to tonight was the
detached C160 (one leg was simply?mechanically loose). It
was not trivial to resolder it, the short leg pretty much
refused to take solder. But I ultimately won.
I got it, I will not change this cap. Equivalents
today seem to require an arm and both legs (except some
surplus?places I know...).
After taking care of C160, this outputs beautifully a
very clean sine. The switches and pots are a bit in need
of TLC, but other than that I'm very happy.?
Thank you all for your input!
Radu.?
On Sun, Sep 25, 2022 at
9:26 PM Froggie the Gremlin < jonpaul@...>
wrote:
what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted
rants.
Clean controls and trimmers
Should be simple to debug
Jon
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.?
Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? Radu.?
Does it look like this?
Glenn
On 9/26/2022 9:28 AM, Radu Bogdan
Dicher wrote:
Hi all,
Does anyone have information on the correct power lamp for
this unit? I can't find that info - all I can find in the
manual is it being a "DS346."
Thank you,
Radu.?
On Sun, Sep 25, 2022 at 10:12
PM Radu Bogdan Dicher via <vondicher= [email protected]>
wrote:
Well, I had no symptoms yet to?file, as until
tonight I didn't get a chance to even plug it in. Visually,
the only?clear issue I was seeing prior to tonight was the
detached C160 (one leg was simply?mechanically loose). It
was not trivial to resolder it, the short leg pretty much
refused to take solder. But I ultimately won.
I got it, I will not change this cap. Equivalents
today seem to require an arm and both legs (except some
surplus?places I know...).
After taking care of C160, this outputs beautifully a
very clean sine. The switches and pots are a bit in need
of TLC, but other than that I'm very happy.?
Thank you all for your input!
Radu.?
On Sun, Sep 25, 2022 at
9:26 PM Froggie the Gremlin < jonpaul@...>
wrote:
what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted
rants.
Clean controls and trimmers
Should be simple to debug
Jon
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
One concern I do have with my grain of rice bulb is it wants 60mA. The entire plugin I recall reading somewhere - can't find it now - needs 70mA, so I'm a bit weary of raising the current through the pass transistors quite a bit. True, I don't know the draw of the original bulbs. Knowing the specs of the original bulbs would help quite a bit. Radu.?
On Mon, Sep 26, 2022 at 5:15 PM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.?
Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? Radu.?
Does it look like this?
Glenn
On 9/26/2022 9:28 AM, Radu Bogdan
Dicher wrote:
Hi all,
Does anyone have information on the correct power lamp for
this unit? I can't find that info - all I can find in the
manual is it being a "DS346."
Thank you,
Radu.?
On Sun, Sep 25, 2022 at 10:12
PM Radu Bogdan Dicher via <vondicher= [email protected]>
wrote:
Well, I had no symptoms yet to?file, as until
tonight I didn't get a chance to even plug it in. Visually,
the only?clear issue I was seeing prior to tonight was the
detached C160 (one leg was simply?mechanically loose). It
was not trivial to resolder it, the short leg pretty much
refused to take solder. But I ultimately won.
I got it, I will not change this cap. Equivalents
today seem to require an arm and both legs (except some
surplus?places I know...).
After taking care of C160, this outputs beautifully a
very clean sine. The switches and pots are a bit in need
of TLC, but other than that I'm very happy.?
Thank you all for your input!
Radu.?
On Sun, Sep 25, 2022 at
9:26 PM Froggie the Gremlin < jonpaul@...>
wrote:
what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted
rants.
Clean controls and trimmers
Should be simple to debug
Jon
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
How could I miss it:
7220 bulb, 26mA?@ 18V...? Radu.?
On Mon, Sep 26, 2022 at 6:20 PM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: One concern I do have with my grain of rice bulb is it wants 60mA. The entire plugin I recall reading somewhere - can't find it now - needs 70mA, so I'm a bit weary of raising the current through the pass transistors quite a bit. True, I don't know the draw of the original bulbs. Knowing the specs of the original bulbs would help quite a bit. Radu.?
On Mon, Sep 26, 2022 at 5:15 PM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.?
Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? Radu.?
Does it look like this?
Glenn
On 9/26/2022 9:28 AM, Radu Bogdan
Dicher wrote:
Hi all,
Does anyone have information on the correct power lamp for
this unit? I can't find that info - all I can find in the
manual is it being a "DS346."
Thank you,
Radu.?
On Sun, Sep 25, 2022 at 10:12
PM Radu Bogdan Dicher via <vondicher= [email protected]>
wrote:
Well, I had no symptoms yet to?file, as until
tonight I didn't get a chance to even plug it in. Visually,
the only?clear issue I was seeing prior to tonight was the
detached C160 (one leg was simply?mechanically loose). It
was not trivial to resolder it, the short leg pretty much
refused to take solder. But I ultimately won.
I got it, I will not change this cap. Equivalents
today seem to require an arm and both legs (except some
surplus?places I know...).
After taking care of C160, this outputs beautifully a
very clean sine. The switches and pots are a bit in need
of TLC, but other than that I'm very happy.?
Thank you all for your input!
Radu.?
On Sun, Sep 25, 2022 at
9:26 PM Froggie the Gremlin < jonpaul@...>
wrote:
what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted
rants.
Clean controls and trimmers
Should be simple to debug
Jon
--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI, FRA, NRA-LM ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"
|
No I have not done any of the low distortion mods to the 502¡¯s in the lab but I am now curious as to what these entail. I popped mine open tonight and found I used a 10K resister to calm the LED down and make it liveable and not eye searingly green. Do you have a link to the low distortion information? ? Zen ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Radu Bogdan Dicher Sent: Monday, September 26, 2022 9:58 PM To: [email protected]Subject: Re: [TekScopes2] SG502 Repair ? How could I miss it: 7220 bulb, 26mA?@ 18V...? ? On Mon, Sep 26, 2022 at 6:20 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: One concern I do have with my grain of rice bulb is it wants 60mA. The entire plugin I recall reading somewhere - can't find it now - needs 70mA, so I'm a bit weary of raising the current through the pass transistors quite a bit. True, I don't know the draw of the original bulbs. Knowing the specs of the original bulbs would help quite a bit. ? On Mon, Sep 26, 2022 at 5:15 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.? Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? ? Does it look like this?
Glenn On 9/26/2022 9:28 AM, Radu Bogdan Dicher wrote: Hi all, Does anyone have information on the correct power lamp for this unit? I can't find that info - all I can find in the manual is it being a "DS346." ? On Sun, Sep 25, 2022 at 10:12 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. ? I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...). After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.? Thank you all for your input! ? On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin <jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
-- ----------------------------------------------------------------------- Glenn Little??????????????? ARRL Technical Specialist?? QCWA? LM 28417 Amateur Callsign:? WB4UIV??????????? wb4uiv@...??? AMSAT LM 2178 QTH:? Goose Creek, SC USA (EM92xx)? USSVI, FRA, NRA-LM??? ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"
|
toggle quoted message
Show quoted text
No I have not done any of the low distortion mods to the 502¡¯s in the lab but I am now curious as to what these entail. I popped mine open tonight and found I used a 10K resister to calm the LED down and make it liveable and not eye searingly green. Do you have a link to the low distortion information? ? Zen ? ? How could I miss it: 7220 bulb, 26mA?@ 18V...? ? On Mon, Sep 26, 2022 at 6:20 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: One concern I do have with my grain of rice bulb is it wants 60mA. The entire plugin I recall reading somewhere - can't find it now - needs 70mA, so I'm a bit weary of raising the current through the pass transistors quite a bit. True, I don't know the draw of the original bulbs. Knowing the specs of the original bulbs would help quite a bit. ? On Mon, Sep 26, 2022 at 5:15 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.? Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? ? Does it look like this?
Glenn On 9/26/2022 9:28 AM, Radu Bogdan Dicher wrote: Hi all, Does anyone have information on the correct power lamp for this unit? I can't find that info - all I can find in the manual is it being a "DS346." ? On Sun, Sep 25, 2022 at 10:12 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. ? I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...). After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.? Thank you all for your input! ? On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin <jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
-- ----------------------------------------------------------------------- Glenn Little??????????????? ARRL Technical Specialist?? QCWA? LM 28417 Amateur Callsign:? WB4UIV??????????? wb4uiv@...??? AMSAT LM 2178 QTH:? Goose Creek, SC USA (EM92xx)? USSVI, FRA, NRA-LM??? ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"
|
Thanks Radu, Ill take a look at this one seems relatively straight forward and reversible, If need be. ? Zen ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Radu Bogdan Dicher Sent: Monday, September 26, 2022 11:19 PM To: [email protected]Subject: Re: [TekScopes2] SG502 Repair ? ? No I have not done any of the low distortion mods to the 502¡¯s in the lab but I am now curious as to what these entail. I popped mine open tonight and found I used a 10K resister to calm the LED down and make it liveable and not eye searingly green. Do you have a link to the low distortion information? ? Zen ? ? How could I miss it: 7220 bulb, 26mA?@ 18V...? ? On Mon, Sep 26, 2022 at 6:20 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: One concern I do have with my grain of rice bulb is it wants 60mA. The entire plugin I recall reading somewhere - can't find it now - needs 70mA, so I'm a bit weary of raising the current through the pass transistors quite a bit. True, I don't know the draw of the original bulbs. Knowing the specs of the original bulbs would help quite a bit. ? On Mon, Sep 26, 2022 at 5:15 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.? Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? ? Does it look like this?
Glenn On 9/26/2022 9:28 AM, Radu Bogdan Dicher wrote: Hi all, Does anyone have information on the correct power lamp for this unit? I can't find that info - all I can find in the manual is it being a "DS346." ? On Sun, Sep 25, 2022 at 10:12 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. ? I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...). After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.? Thank you all for your input! ? On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin <jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
? -- ----------------------------------------------------------------------- Glenn Little??????????????? ARRL Technical Specialist?? QCWA? LM 28417 Amateur Callsign:? WB4UIV??????????? wb4uiv@...??? AMSAT LM 2178 QTH:? Goose Creek, SC USA (EM92xx)? USSVI, FRA, NRA-LM??? ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"
|
Well, it looks like LED it is (see? /g/TekScopes2/photo/278771/3494775?p=Created%2C%2C%2C20%2C2%2C0%2C0, where the solder looks dull, which is some artifact of the picture).? Anyway, I think this is a very neat solution. A 3mm LED is about the size of a grain-of-rice. I had the opposite experience than Zen, I had to lower the R to 1k (I'd have gone lower, but I'd get into power resistor territory), for about 18mA through?the LED. Even so, there's not much light coming through, and it may just be the LEDs I have at hand (and maybe the "density" of the green jewel?). These were just vanilla?green 3mm LEDs I had at?hand.?
Supply to bulb reverses polarity (C5/279) Much more importantly, though, for anyone doing?this down the line, there's a Manual Change (Reference C5/279), which?is only available at the Boat Anchor Archive, which reverses?where the light bulb attaches - instead of the positive rail it goes to the negative. So a good idea is to check if your unit has this implemented.?
I initially?polarized the LED as per the main schematic, and upon it not turning on and seeing it not lit, I realized I've previously glanced at the revision?(last page on the BAMA PDF). So I had to unsolder and reverse it.?
Radu.?
Thanks Radu, Ill take a look at this one seems relatively straight forward and reversible, If need be. ? Zen ? ? ? No I have not done any of the low distortion mods to the 502¡¯s in the lab but I am now curious as to what these entail. I popped mine open tonight and found I used a 10K resister to calm the LED down and make it liveable and not eye searingly green. Do you have a link to the low distortion information? ? Zen ? ? How could I miss it: 7220 bulb, 26mA?@ 18V...? ? On Mon, Sep 26, 2022 at 6:20 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: One concern I do have with my grain of rice bulb is it wants 60mA. The entire plugin I recall reading somewhere - can't find it now - needs 70mA, so I'm a bit weary of raising the current through the pass transistors quite a bit. True, I don't know the draw of the original bulbs. Knowing the specs of the original bulbs would help quite a bit. ? On Mon, Sep 26, 2022 at 5:15 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Zen - glad to see you here! Yes, a very cute unit. I'm looking forward to checking it closer against?my instrumentation - such as looking at its distortion through the AP S1. Also, checking the levels and all that (though this far it looks absolutely dead on). Calibrate it, if it needs it. Have you done the?"low distortion mods," I'm curious?....? The LED suggestion is a very good idea, I may go that way.? Glenn - no, the bulb looks like a legged... whatchumacallit - "grain-of-rice" bulb? I do have some Radioshack #7219s, though I may have to change the series?resistor if I use one of those. They do have 10,000hrs average life, so not a bad option.? ? Does it look like this?
Glenn On 9/26/2022 9:28 AM, Radu Bogdan Dicher wrote: Hi all, Does anyone have information on the correct power lamp for this unit? I can't find that info - all I can find in the manual is it being a "DS346." ? On Sun, Sep 25, 2022 at 10:12 PM Radu Bogdan Dicher via <vondicher=[email protected]> wrote: Well, I had no symptoms yet to?file, as until tonight I didn't get a chance to even plug it in. Visually, the only?clear issue I was seeing prior to tonight was the detached C160 (one leg was simply?mechanically loose). It was not trivial to resolder it, the short leg pretty much refused to take solder. But I ultimately won. ? I got it, I will not change this cap. Equivalents today seem to require an arm and both legs (except some surplus?places I know...). After taking care of C160, this outputs beautifully a very clean sine. The switches and pots are a bit in need of TLC, but other than that I'm very happy.? Thank you all for your input! ? On Sun, Sep 25, 2022 at 9:26 PM Froggie the Gremlin <jonpaul@...> wrote: what is symptom?
never replace timing caps
suspect the usual range switches, possible PS shorted rants.
Clean controls and trimmers
Should be simple to debug
Jon
? -- ----------------------------------------------------------------------- Glenn Little??????????????? ARRL Technical Specialist?? QCWA? LM 28417 Amateur Callsign:? WB4UIV??????????? wb4uiv@...??? AMSAT LM 2178 QTH:? Goose Creek, SC USA (EM92xx)? USSVI, FRA, NRA-LM??? ARRL TAPR "It is not the class of license that the Amateur holds but the class of the Amateur that holds the license"
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I like to use high brightness LED's with a current limiting resistor sized to bring the brightness waaaay way down.
I have found that often with 'normal' brightness LED's, the colour doesn't shine through very well due to the colour mismatch between the green of the LED and the green of the jewel in the lamp holder.
I currently use green LED's that put out 5000mcd, then use an appropriate resistor I chose by checking the LED brightness by eye, usually it means the LED is consuming around low single-digit milliamps or so.
P.s. The SG502 manual at Tekwiki also has the manual change info re. the polarity change of the lamp.
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Jared, You're right on the Tekwiki version having that. I guess when I printed out my copy I must have misplaced the addendums when binding it.? That said (and out of context with the above), the BAMA version has the edge of having all schematics?on their own page which is a big advantage to me. I'm happy to pay Artek for manuals just to get schematics and diagrams on large pages, which I am able to print tabloid at home.? Radu.?
On Tue, Sep 27, 2022 at 5:18 PM Jared Cabot via <jaredcabot= [email protected]> wrote: I like to use high brightness LED's with a current limiting resistor sized to bring the brightness waaaay way down.
I have found that often with 'normal' brightness LED's, the colour doesn't shine through very well due to the colour mismatch between the green of the LED and the green of the jewel in the lamp holder.
I currently use green LED's that put out 5000mcd, then use an appropriate resistor I chose by checking the LED brightness by eye, usually it means the LED is consuming around low single-digit milliamps or so.
P.s. The SG502 manual at Tekwiki also has the manual change info re. the polarity change of the lamp.
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A further note on this - Jared, you're spot on with your observation on the color mismatch, and such a pertinent point to make.
I assume, as LEDs are pretty "narrowband" light emitting devices, the dissimilar wavelength of my picked green LED and the actual filter on the plugin is indeed a dealbreaker. I switched to a white LED - I haven't specifically?looked into their specs, but they implicitly are "wideband," so there's far more light of appropriate wavelength being generated, to penetrate the?jewel/filter.?
If anything, it's very bright now and I may have to dial it down a bit with the series resistor, but it doesn't bother me too much. I assume the original light must have been pretty conspicuous itself. I can tell when it's on regardless of the ambient light, which is the exact goal here, and for well under 20mA, which is a nice?bonus.?
On Tue, Sep 27, 2022 at 9:24 PM Radu Bogdan Dicher via <vondicher= [email protected]> wrote: Jared, You're right on the Tekwiki version having that. I guess when I printed out my copy I must have misplaced the addendums when binding it.? That said (and out of context with the above), the BAMA version has the edge of having all schematics?on their own page which is a big advantage to me. I'm happy to pay Artek for manuals just to get schematics and diagrams on large pages, which I am able to print tabloid at home.? Radu.?
On Tue, Sep 27, 2022 at 5:18 PM Jared Cabot via <jaredcabot= [email protected]> wrote: I like to use high brightness LED's with a current limiting resistor sized to bring the brightness waaaay way down.
I have found that often with 'normal' brightness LED's, the colour doesn't shine through very well due to the colour mismatch between the green of the LED and the green of the jewel in the lamp holder.
I currently use green LED's that put out 5000mcd, then use an appropriate resistor I chose by checking the LED brightness by eye, usually it means the LED is consuming around low single-digit milliamps or so.
P.s. The SG502 manual at Tekwiki also has the manual change info re. the polarity change of the lamp.
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Froggie the Gremlin
Jared Cabot