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G'day y'all.? So the SX-16 was wrapped up, just about, with the bottom cover put back in place and a final IF/RF alignment done.? Spent a good part of last evening SWLing and tuning in 20M and 40M SSB rag-chewing.
Next day I fire it up and there is an awful loud cacophony of snaps, crackles and pops emanating from the speaker.? The level of that csp does not change with AF or RF gain control, just as loud with both turned to minimum.
Other than the csp noise all functions operate as expected, even the top two bands pull in CB'rs (oh joy!) and 6M SSB on just the test bench long wire.
Yes, a complete electro/wax/mica cap replacement had been done, any resistor over or approaching 20% out of spec replaced, etc, etc.?
Monitoring the B+ it seems a steady 310v DC after a short warm up. (Variac is at 115vac.)
I swapped the 5881's (that it came with in place of the 6V6G's), swapped the 6R7 (as it's the first audio amp), no change.?
With the 2nd IF amp 6K7 removed the noise is still there confirming it's after that (or supply related).
I even pulled the cover off of T4 to look at those top mounted trimmers, very clean and looked fine to me. (Even tho it sort of resembles that kind of noise, I usually don't suspect an SMD issue with such trimmers anyways.)?
Went after a couple of the remaining ceramic picofarad caps around the AVC/1st audio section, no change to noise. (The SX-25 developed same issue after a year's use and that was a mica I had left in that same area.)
Voltage checks are within those listed on the SX-16 chart with the exception of the screen voltage on the 5881's, pin 4 is at 290v where the chart shows 275v for a pair of 6V6's.? But the 5881's have a higher screen voltage rating anyway. ?
The amount of noise seems to lessen after the receiver is left on awhile but never lessens in volume or goes away.
I dread it being one of the audio transformers but could it be??
Searched this forum and I found Bill's SX-17 posting with apparently same issue but could not find any follow up to it.? So, Bill, ever resolve? (oh please, oh please have a simple fix!)
I'm all ears to any suggestions.?
--
Dan
K1DTS
|
Do you have a scope? If so do some signal tracing. \
The only schematic I can find shows the audio output stage to be a
push-pull pentode stage driven via a grid transformer from a 6R7, a dual
diode, triode. The diodes are in parallel and are used as the detector.
The triode is the first audio, it drives the output amp via a
transformer. The audio gain is in the grid of the 6R7. Since the noise
does not vary with the gain control it is coming from the audio stage.
The headphone jack is arranged so that the phones are connected to the
output of the 6R7 through the driver transformer, that is, the grid
drive of the output stage. See if you are getting the noise at the jack.
This is the output of the driver transformer. If not the noise is coming
from the output stage or power supply.
I am not sure from your post if you put 6V6 tubes in the amplifier.
That is what should be in there. A 5881 is a variation of a 6L6 designed
to take higher screen voltage, While they might work in place of 6V6
tubes they might also draw too much current. If you just changed tubes
try another set, one of the replacements might be bad. You can run the
output amp with only one tube briefly to see if the popping is
associated with one of the tubes. Since the 5881 tubes were in there it
probably safe to put them back in to see if they are noise free.
Did you replace the filter caps? In any case I would check them.
Also R-29, the dropping resistor for the driver transformer which is
also part of the B+ filter. There is really not a lot there. Good luck,
its a beautiful receiver.
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On 10/31/2024 7:18 PM, dtssr via groups.io wrote: G'day y'all.? So the SX-16 was wrapped up, just about, with the bottom
cover put back in place and a final IF/RF alignment done.? Spent a good
part of last evening SWLing and tuning in 20M and 40M SSB rag-chewing.
Next day I fire it up and there is an awful loud cacophony of snaps,
crackles and pops emanating from the speaker.? The level of that csp
does not change with AF or RF gain control, just as loud with both
turned to minimum.
Other than the csp noise all functions operate as expected, even the top
two bands pull in CB'rs (oh joy!) and 6M SSB on just the test bench long
wire.
Yes, a complete electro/wax/mica cap replacement had been done, any
resistor over or approaching 20% out of spec replaced, etc, etc.
Monitoring the B+ it seems a steady 310v DC after a short warm up.
(Variac is at 115vac.)
I swapped the 5881's (that it came with in place of the 6V6G's), swapped
the 6R7 (as it's the first audio amp), no change.
With the 2nd IF amp 6K7 removed the noise is still there confirming it's
after that (or supply related).
I even pulled the cover off of T4 to look at those top mounted trimmers,
very clean and looked fine to me. (Even tho it sort of resembles that
kind of noise, I usually don't suspect an SMD issue with such trimmers
anyways.)
Went after a couple of the remaining ceramic picofarad caps around the
AVC/1st audio section, no change to noise. (The SX-25 developed same
issue after a year's use and that was a mica I had left in that same area.)
Voltage checks are within those listed on the SX-16 chart with the
exception of the screen voltage on the 5881's, pin 4 is at 290v where
the chart shows 275v for a pair of 6V6's.? But the 5881's have a higher
screen voltage rating anyway.
The amount of noise seems to lessen after the receiver is left on awhile
but never lessens in volume or goes away.
I dread it being one of the audio transformers but could it be?
Searched this forum and I found Bill's SX-17 posting with apparently
same issue but could not find any follow up to it.? So, Bill, ever
resolve? (oh please, oh please have a simple fix!)
I'm all ears to any suggestions.
--
Dan
K1DTS
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
The noise is still present when using an old set of Halli phones.
It was easier to just pull and run with one 5881, power up and the noise was there, then reinstall and repeat with the other.?
I do not have a pair of 6V6's to swap in, I've only one in the spares.? I eventually dug out and tried another pair of 5881's, no change.
Filter caps where replaced with a pair of 22uf's @ 450v.? The C40 10uf at cathode of the 6R7 replaced with a 10uf @ 400v.
R29 10K was replaced first go thru being over tolerance.?
?
Started at the supply side. (Since 6V6's are referenced in the prints I'll refer to the present 5881's as 6V6's)? SX-16 audio section attached to message.
Scope set at .2v per, AC coupling, looking for noise, none seen at "bottom" T5 primary & R29, C46 junction.
290v at C44 and 6V6-4 screens is steady and no noise.
C45 and the center tap of T6, there is a 30v ripple on the DC but no noise.
The 6R7-4,5 diodes, it's grid cap at center tap of the AFG pot, no noise.
The "top" of T5 primary & 6R7-3 plate there's plenty of noise and, of course, that shows up on the secondary and 6V6 grids thru to output.
I don't have another 6R7 to sub in there (or if there's one in another of the 25 receivers) but do have a 6T7 somewhere according to my inventory sheet. Nostalgia Air shows that tube is a valid swap but I'll compare specs before trying this evening.
At first the rig was fairly quiet noise wise this morning, the csp was little to almost not there. Gave an opportunity to wiggle and tap about to see if I could aggravate the problem, no such luck.
I had to power cycle it a few times to ring out connections and trace wires.? Sometimes the snap and pops are awfully loud and deafening, other times its just the annoying crackle and sizzle sound.
Leaning towards that 6R7 myself.
?
--
Dan
K1DTS
|
Dan, it seems that you are doing an admirable job of tracing and documenting. It seems that the 6R7 ?area it the problem area.? I may have missed something but have you considered the cathode cap for the? 6R7? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of dtssr via groups.io
Sent: Friday, November 1, 2024 12:43 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21? The noise is still present when using an old set of Halli phones. It was easier to just pull and run with one 5881, power up and the noise was there, then reinstall and repeat with the other.? I do not have a pair of 6V6's to swap in, I've only one in the spares.? I eventually dug out and tried another pair of 5881's, no change. Filter caps where replaced with a pair of 22uf's @ 450v.? The C40 10uf at cathode of the 6R7 replaced with a 10uf @ 400v. R29 10K was replaced first go thru being over tolerance.? Started at the supply side. (Since 6V6's are referenced in the prints I'll refer to the present 5881's as 6V6's)? SX-16 audio section attached to message. Scope set at .2v per, AC coupling, looking for noise, none seen at "bottom" T5 primary & R29, C46 junction. 290v at C44 and 6V6-4 screens is steady and no noise. C45 and the center tap of T6, there is a 30v ripple on the DC but no noise. The 6R7-4,5 diodes, it's grid cap at center tap of the AFG pot, no noise. The "top" of T5 primary & 6R7-3 plate there's plenty of noise and, of course, that shows up on the secondary and 6V6 grids thru to output. I don't have another 6R7 to sub in there (or if there's one in another of the 25 receivers) but do have a 6T7 somewhere according to my inventory sheet. Nostalgia Air shows that tube is a valid swap but I'll compare specs before trying this evening. At first the rig was fairly quiet noise wise this morning, the csp was little to almost not there. Gave an opportunity to wiggle and tap about to see if I could aggravate the problem, no such luck. I had to power cycle it a few times to ring out connections and trace wires.? Sometimes the snap and pops are awfully loud and deafening, other times its just the annoying crackle and sizzle sound. Leaning towards that 6R7 myself. -- don??? va3drl
|
The 6R7GT grid cap was reworked earlier. The shield loom had previously been badly kinked and was breaking up.? So I cut back one inch, pushed the loom back a bit, slid a length of heatshrink over the loom, stripped and insulated the conductor wire with appropriate sized heatshrink.? Re-crimped and soldered the cap on the conductor, slid and shrunk the outer shrink into place.? I just now found that earlier work resulted in a grid wire just a bit to short to reach the cap on the taller 6T7G I put in place to test with but rigged up a short clip to span the gap.?
No change to SCP noise symptoms with that tube in place, I put the 6R7GT back in.
?
Dan
K1DTS
|
The 6R7 and 6T7 are rather different although they have the same
base and grid connections. One will do for trouble shooting the other
but the triode characteristics are rather different. Also, the envelopes
are of different sizes, a 6T7 may not fit in place of a 6R7. However, if
one is easily available give it a try. The noise could be caused by the
tube.
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On 11/1/2024 9:43 AM, dtssr via groups.io wrote:
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
|
|
Dan,?? Getting late, don’t know if you have it fixed. My past question was about the cathode cap-ACITOR, but anyhow the cathode of the 6R7 has a lot of stuff dangling on it, including SW3 if I see correctly. ?Anything mucking up the cathode will be seen at the plate and onwards. I have not seen any comment on the cathode, and any noise on it. If there is it MIGHT come from various. Maybe you can remove a bunch as a test?.. leaving the cathode bias resistor and cap. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of dtssr via groups.io
Sent: Friday, November 1, 2024 6:24 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21? The 6R7GT grid cap was reworked earlier. The shield loom had previously been badly kinked and was breaking up.? So I cut back one inch, pushed the loom back a bit, slid a length of heatshrink over the loom, stripped and insulated the conductor wire with appropriate sized heatshrink.? Re-crimped and soldered the cap on the conductor, slid and shrunk the outer shrink into place.? I just now found that earlier work resulted in a grid wire just a bit to short to reach the cap on the taller 6T7G I put in place to test with but rigged up a short clip to span the gap.? No change to SCP noise symptoms with that tube in place, I put the 6R7GT back in. -- don??? va3drl
|
Thanks for following up, much appreciated.?
The 10mfd@25v at the cathode pin 8 was replaced, I think I left the 950 ohm R25 in place as it was not far off in value (or I put a 1K in there, I have to check).? My notes from scoping out that section show "6R7, 8, no noise".? I didn't try isolating by lifting anything to open circuits yet but it is next steps.? Notes also show no noise was present on the pair of 6V6 pin 4 screen grids as well.? So for removing, I guess start steps at the 6R7 plate, C41, C43, etc. "isolating" the amp section and what ties into the T5 primary. Problem's either on one side or the other.
I set the unit aside last week as I needed to get away from it and work on something easy.? The noise it emits while working on it can be nerve wracking (I'm using a 5K to 4 ohm trans to drive a bench speaker and added a pot to the speaker side to shunt the noise somewhat).? I moved on to knock out a GE-L630 AA5 confidence builder I might keep for the collection rather than flip.? Once the bench is clear I'll put the SX-16 back "under the scope."? There's an SX-9 in the Halli queue and still the poor 'ol S-20R that's been in the shed for a year.?
--
Dan
K1DTS
|
Dan, Good to take a break and start later with fresh eyes. Following your answer [the cathode shows no noise], my simple conclusion is that the 6R7 plate is generating noise all by itself, but you effectively tested that with the other tube. So maybe the noise generator is closer to T5 perhaps a bad wire, I don’t want to say ?an erratic short in the primary or T5, but it is hard to rule that out. Did you consider removing the 6R7?.. which should silence the noise, then maybe bypass the tube with a resistor from B+ to T5 top and or the same but ?with the resistor going to only T5,, all depending on the actual wiring.?? OK back to the break Dan ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Daniel K1DTS via groups.io
Sent: Thursday, November 14, 2024 11:08 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21? Thanks for following up, much appreciated.? The 10mfd@25v at the cathode pin 8 was replaced, I think I left the 950 ohm R25 in place as it was not far off in value (or I put a 1K in there, I have to check).? My notes from scoping out that section show "6R7, 8, no noise".? I didn't try isolating by lifting anything to open circuits yet but it is next steps.? Notes also show no noise was present on the pair of 6V6 pin 4 screen grids as well.? So for removing, I guess start steps at the 6R7 plate, C41, C43, etc. "isolating" the amp section and what ties into the T5 primary. Problem's either on one side or the other. I set the unit aside last week as I needed to get away from it and work on something easy.? The noise it emits while working on it can be nerve wracking (I'm using a 5K to 4 ohm trans to drive a bench speaker and added a pot to the speaker side to shunt the noise somewhat).? I moved on to knock out a GE-L630 AA5 confidence builder I might keep for the collection rather than flip.? Once the bench is clear I'll put the SX-16 back "under the scope."? There's an SX-9 in the Halli queue and still the poor 'ol S-20R that's been in the shed for a year.? -- don??? va3drl
|
I wiggled and moved every wire, socket, terminal strip, etc. trying to source a perhaps bad wire or connection between the 6R7 and final output.?
Even freeze spray and heat on those area components under chassis that I didn't change out attempting to change symptoms and narrow down.?
It'll be back on the bench tomorrow.
Did you consider removing the 6R7?.. which should silence the noise, then maybe bypass the tube with a resistor from B+ to T5 top
Referencing the schematic snip from an earlier post above.?
If I follow you, pull the 6R7 (which I did previously and, yes, there was clean silence).
Lift and isolate the lead going to top of T5 primary that the 6R7 output plate (pin 3) feeds.?
Tack a resistor from the B+ (CH1 choke/C44 which is same as 6V6 screen grids) to the loose T5 lead. ?I'd think a 2k ohm 1 or 2W should do for a very brief check. ?
This divides the 6R7 and it's dangling stuff on one side leaving T5 and 6V6's on the other.? Makes sense, your supplying T5 with a different source other than the 6R7 plate.
If YES there is SCP noise, the cause is on the amp side, likely T5 arcing.? :-( ?
?
?
--
Dan
K1DTS
|
Dan yes, or something like that. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Daniel K1DTS via groups.io
Sent: Thursday, November 14, 2024 8:37 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21? I wiggled and moved every wire, socket, terminal strip, etc. trying to source a perhaps bad wire or connection between the 6R7 and final output.? Even freeze spray and heat on those area components under chassis that I didn't change out attempting to change symptoms and narrow down.? It'll be back on the bench tomorrow. Did you consider removing the 6R7?.. which should silence the noise, then maybe bypass the tube with a resistor from B+ to T5 top Referencing the schematic snip from an earlier post above.? If I follow you, pull the 6R7 (which I did previously and, yes, there was clean silence). Lift and isolate the lead going to top of T5 primary that the 6R7 output plate (pin 3) feeds.? Tack a resistor from the B+ (CH1 choke/C44 which is same as 6V6 screen grids) to the loose T5 lead. ?I'd think a 2k ohm 1 or 2W should do for a very brief check. ? This divides the 6R7 and it's dangling stuff on one side leaving T5 and 6V6's on the other.? Makes sense, your supplying T5 with a different source other than the 6R7 plate. If YES there is SCP noise, the cause is on the amp side, likely T5 arcing.? :-( ? -- don??? va3drl
|
And if the T5 seems ok , using the same split idea,?? power the 6R7 from B+[ sort of] through a temp PLATE RESISTOR , rather than ?using T5 and see what happens. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of don Root
Sent: Thursday, November 14, 2024 8:48 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21? Dan yes, or something like that. ? From: [email protected] [mailto:[email protected]] On Behalf Of Daniel K1DTS via groups.io
Sent: Thursday, November 14, 2024 8:37 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21 ? I wiggled and moved every wire, socket, terminal strip, etc. trying to source a perhaps bad wire or connection between the 6R7 and final output.? Even freeze spray and heat on those area components under chassis that I didn't change out attempting to change symptoms and narrow down.? It'll be back on the bench tomorrow. Did you consider removing the 6R7?.. which should silence the noise, then maybe bypass the tube with a resistor from B+ to T5 top Referencing the schematic snip from an earlier post above.? If I follow you, pull the 6R7 (which I did previously and, yes, there was clean silence). Lift and isolate the lead going to top of T5 primary that the 6R7 output plate (pin 3) feeds.? Tack a resistor from the B+ (CH1 choke/C44 which is same as 6V6 screen grids) to the loose T5 lead. ?I'd think a 2k ohm 1 or 2W should do for a very brief check. ? This divides the 6R7 and it's dangling stuff on one side leaving T5 and 6V6's on the other.? Makes sense, your supplying T5 with a different source other than the 6R7 plate. If YES there is SCP noise, the cause is on the amp side, likely T5 arcing.? :-( ? -- don??? va3drl
|
I think I suggested this already, if so forgive the repetition.
There are a couple of places you can check the signal flow. Especially
if you have a scope. The grid drive for the 6V6 output tubes is via a
transformer. Its primary is in the plate of the 6R7. This is a dual
diode/triode where the diodes are connected in parallel to form the
detector and the triode is the first audio and driver for the output
stage. One side of the driver transformer output is connected to the
headphone jack and drives the headphones. When headphones are connected
they operate a switch which disconnects the loudspeaker. For some reason
Hallicrafters liked this arrangement. The headphones must be of the high
impedance variety. In any case, if the noise is heard in the headphones
its coming from the 6R7 or before it or the driver transformer. The
headphones should work with the 6V6 tubes removed.
If you have a scope look at the plate of the 6R7. Actually, if the
noise is due to arcing in T-5 it may show up there. I would see if its
there with the 6R7 removed. Also, the 6J7 S-meter amplifier goes to the
cathodes of the 6V6 tubes and may be introducing noise if something is
arcing there.
Very curious problem and I am interested to find out what you learn.
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On 11/14/2024 5:37 PM, Daniel K1DTS via groups.io wrote: I wiggled and moved every wire, socket, terminal strip, etc. trying to
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Dan,? was tossing in bed, and I realized that I had two ideas, and got them mixed up while writing. For testing T5, if you can open/lift the top wire, then insert a resistor going to ?ground [B-minus] not B+ to act as the plate load. B+ is on the other side of the transformer. ?I don’t have values in my head, but ?I.m sure you will come up with something. My use of “B+” is loose, and I have not looked closely.? Sorry for the confusion. They say “check your writing, and thinking three times before publishing”, but I keep forgetting that. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of don Root
Sent: Thursday, November 14, 2024 8:48 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21? Dan yes, or something like that. ? From: [email protected] [mailto:[email protected]] On Behalf Of Daniel K1DTS via groups.io
Sent: Thursday, November 14, 2024 8:37 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] SX-16 with snap, crackle, pop ( Bill's beloved SX-17 on the ropes 03/06/21 ? I wiggled and moved every wire, socket, terminal strip, etc. trying to source a perhaps bad wire or connection between the 6R7 and final output.? Even freeze spray and heat on those area components under chassis that I didn't change out attempting to change symptoms and narrow down.? It'll be back on the bench tomorrow. Did you consider removing the 6R7?.. which should silence the noise, then maybe bypass the tube with a resistor from B+ to T5 top Referencing the schematic snip from an earlier post above.? If I follow you, pull the 6R7 (which I did previously and, yes, there was clean silence). Lift and isolate the lead going to top of T5 primary that the 6R7 output plate (pin 3) feeds.? Tack a resistor from the B+ (CH1 choke/C44 which is same as 6V6 screen grids) to the loose T5 lead. ?I'd think a 2k ohm 1 or 2W should do for a very brief check. ? This divides the 6R7 and it's dangling stuff on one side leaving T5 and 6V6's on the other.? Makes sense, your supplying T5 with a different source other than the 6R7 plate. If YES there is SCP noise, the cause is on the amp side, likely T5 arcing.? :-( ? -- don??? va3drl
|
Thanks to the both of you.? I'll be back at it this evening, great to have your inputs and experience to aid me and push me along.?
Ah, yes, the S meter 6J7, I can open a lead on the R30 zero pot to cut that out and give a listen.? Earlier I posted "The noise is still present when using an old set of Halli phones." but I had the 6V6 pair in place as the phones jack switch "removes" them and T6.? (Leaving the issue T5 and what's tied to its primary.)? I'll repeat but without the pair in place and probe with the scope.???
Attached is a short video of the rig, listening to weather reports on SSB, note when the AF & RF are turned down.? No "jump out of my seat" loud popping during the recording but the snap and crackle is there.
Will report back in a day or so.
--
Dan
K1DTS
|
The file I forgot to attach.
--
Dan
K1DTS
|
There is no joy in Mudville tonight.
?
Noise with the headphones plugged in, Yes.? Easy to see with scope at C64 feeding the jack tip.
Noise with the headphones and the 6V6's removed, Yes.
Noise at the plate of the 6R7 and T5 junction, Yes.
Noise at the plate of 6R7 without the connection to top of T5 in place, No.? A steady -.77v.
Noise at the unconnected top terminal of T5, Yes.? And bottom (@ R29/C46 tie point).
Headphones don't work now, using scope is difficult as there is now so much fluctuation in the trace (Ch1) no matter what I try to sync Ch2 to.
Removed the "S meter" tie at R30 (but think the 6V6 removal achieves same.? If anything, further removes T5 secondary and 6V6 sockets.)
At the terminal strip holding R29 10K & C46 1mfd, lifted the B+ wire coming up from C44 and Ch1 choke.? This remove B+ feed to remainder of chassis.? Milli-volts of noise seen at open top of T5 terminal, and bottom (R29/C46).
At that point there's nothing driving T5, it's just a conductor for the most part.? The power supply is all that's left.
Replaced both C44, C45 filter caps as I had done during the recapping, using 22Mfd @ 450v.
I don't have a spare 5Z3. (SX-11 has one but I'm not pulling one out of the other working receivers.)
Cobbled together a solid state replacement for the 5Z3, tacked it in bottom side to the empty socket.? No change. ?
(Didn't add the usual CL-140 so just very gradually turned up the variac when powering up.? Also, no need to apply beyond 60VAC before you can see/hear the noise.)
Pulled the Ch1 choke and replaced with a 2K 10W, no change to what I can see on the scope.
Tacked the loose wires back into place to verify I can still hear noise in headphones, receive stations, Yes.? Good, I didn't make it worse.
Pulled the SS replacement 53Z, put the tube back in, put the choke back in, put the 6V6s back in, verified receiver works as it had prior to my hacks and still painfully loud SCP over the speaker.
?
When I next get to it, I have a PT I can wire in for the mounted transformer T7, one heavy 320-0-320/5v4A/6.3v4A with nice long leads I use to bench test with.?
If the PT is the culprit I've Xfers from a SX43 & 110 that should fit.
?
?
--
Dan
K1DTS
|
Connection to "top" of T-5. If removed there is no B+ on tube. Will
also kill headphone output.
Have you taken out the 6V6's and left the headphones connected?
Should still have noise or audio. If you disconnect both at once you
should still see noise or audio at the headphone jack, which is the
output of one side of T-5, to the grid of the lower 6V6. Won't matter if
the 6V6 is pulled out. If the noise is there its likely coming from the
transformer.
Not sure how you are getting noise at the plate of the 6R7 with the
lead to the transformer disconnected since there is no B+ there.
Check with everything connected by the 6R7 removed. If noise at the
plate lead its from the transformer, perhaps arcing. However, since
there is no current trough the transformer its possible it may not arc.
However, more confusion: if you get the noise at the power supply
side of T-5, with the load side disconnected its possible it may be
arcing in T-5 or its coming from the power supply. Disconnect T-5 from
R-29 and see what you get at that junction. Could be arcing at the
resistor or filter cap. T-5 won't make noise with no voltage on it.
Do the headphones not work at all? What have you done there? If
something else is disconnected or tube removed there may not be a signal
there. If all is normal there should be drive to the headphones but the
switch in the jack may be bad.
Please clarify, you have confused me.
I am not trimming this thread so others (and me) will know what we
are talking about.
v
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On 11/17/2024 4:25 PM, Daniel K1DTS via groups.io wrote: There is no joy in Mudville tonight.
Noise with the headphones plugged in, Yes.? Easy to see with scope at
C64 feeding the jack tip.
Noise with the headphones and the 6V6's removed, Yes.
Noise at the plate of the 6R7 and T5 junction, Yes.
Noise at the plate of 6R7 without the connection to top of T5 in place,
No.? A steady -.77v.
Noise at the unconnected top terminal of T5, Yes.? And bottom (@ R29/C46
tie point).
Headphones don't work now, using scope is difficult as there is now so
much fluctuation in the trace (Ch1) no matter what I try to sync Ch2 to.
Removed the "S meter" tie at R30 (but think the 6V6 removal achieves
same.? If anything, further removes T5 secondary and 6V6 sockets.)
At the terminal strip holding R29 10K & C46 1mfd, lifted the B+ wire
coming up from C44 and Ch1 choke.? This remove B+ feed to remainder of
chassis.? Milli-volts of noise seen at open top of T5 terminal, and
bottom (R29/C46).
At that point there's nothing driving T5, it's just a conductor for the
most part.? The power supply is all that's left.
Replaced both C44, C45 filter caps as I had done during the recapping,
using 22Mfd @ 450v.
I don't have a spare 5Z3. (SX-11 has one but I'm not pulling one out of
the other working receivers.)
Cobbled together a solid state replacement for the 5Z3, tacked it in
bottom side to the empty socket.? No change.
(Didn't add the usual CL-140 so just very gradually turned up the variac
when powering up.? Also, no need to apply beyond 60VAC before you can
see/hear the noise.)
Pulled the Ch1 choke and replaced with a 2K 10W, no change to what I can
see on the scope.
Tacked the loose wires back into place to verify I can still hear noise
in headphones, receive stations, Yes.? Good, I didn't make it worse.
Pulled the SS replacement 53Z, put the tube back in, put the choke back
in, put the 6V6s back in, verified receiver works as it had prior to my
hacks and still painfully loud SCP over the speaker.
When I next get to it, I have a PT I can wire in for the mounted
transformer T7, one heavy 320-0-320/5v4A/6.3v4A with nice long leads I
use to bench test with.
If the PT is the culprit I've Xfers from a SX43 & 110 that should fit.
--
Dan
K1DTS
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard, first thank-you, I much appreciate you and your quick reply.
- Your inquires in blue, my reply's in black.
?
Have you taken out the 6V6's and left the headphones connected?
Noise with the headphones and the 6V6's removed, Yes.
Should still have noise or audio. If you disconnect both at once you
should still see noise or audio at the headphone jack, which is the
output of one side of T-5, to the grid of the lower 6V6. Won't matter if
the 6V6 is pulled out.
Noise with the headphones plugged in, Yes. ?Easy to see with scope at C64 feeding the jack tip.
If the noise is there its likely coming from the
transformer.
If only I had a replacement to try.
Not sure how you are getting noise at the plate of the 6R7 with the
lead to the transformer disconnected since there is no B+ there.
I stated: Noise at the plate of 6R7 without the connection to top of T5 in place, No.
I should have led that sentence with the "No" , my bad.
However, more confusion: if you get the noise at the power supply
side of T-5, with the load side disconnected its possible it may be
arcing in T-5 or its coming from the power supply. Disconnect T-5 from
R-29 and see what you get at that junction.
The top of T5 primary was open, not any other connection there, and there was noise seen with the scope both there and at the R29/C46 bottom end of T5 primary, the supply side.
I did not disconnect R29 during any tracing.
In the snippet below, the red lines indicate the open points isolating T5 from 6R7 and supply B+ from everywhere else.? (6V6's pulled, S meter R30 opened... ) ?
What I reported - At the terminal strip holding R29 10K & C46 1mfd, I lifted the B+ wire coming up from C44 and Ch1 choke. ?This removed B+ feed to remainder of chassis. ?
Milli-volts of noise seen at open top of T5 terminal, and bottom (R29/C46).? At that point there's nothing driving T5, it's just a conductor for the most part. ?The power supply is all that's left.
?
?
Could be arcing at the resistor or filter cap. T-5 won't make noise with no voltage on it.
(R29 10K was replaced along with C46 during the earlier recapping as being out of tolerance.)
Do the headphones not work at all?
As stated , they do work, I used in place of speaker to troubleshoot so as not to be blasted by the noise.? That is up until T5 primary was lifted.
?
As an early suspect, if I had a T5 (A4826 printed on the side) I'd have slipped it in a week ago.? I realize I might just be chasing ghost transients at this point.? I'm working with what I have and I have power transformers.? If the only thing left is a part I don't have, well that narrows it down too.
?
--
Dan
K1DTS
|
don Root