Hmmmmm...so Rick...that "broken resistor(?)" in your RV-75 that we thought was a 10 Kohm.....didn't it have a beige body?
This complicates things a bit!
73 Peter VE7PS
On Fri, Feb 2, 2024 at 10:08?AM Jim Shorney < jimNU0C@...> wrote:
Based on what Mr. Google is showing me they are axial ceramic capacitors. I'm thinking now that the pink ones are also. That would explain the schematic discrepancies. I don't think I have ever heard of any failing.
73
-Jim
NU0C
On Fri, 02 Feb 2024 09:32:15 -0800
"Rick K8EZB" <frboswell@...> wrote:
> Identifying RV75 capacitors:
>
> The components in the photo below include both resistors and capacitors on the RV75 RF & Analog board, with the capacitors having the beige colored body and are designated on the ckt diag as C224, C225 etc. I am not familiar with this type of capacitor; a link to online info appreciated. The RV75 boards have many of this type of capacitor, the failure of which can cause much difficulty.
>
> Thanks,
> Rick
> K8EZB
>
>
>
>
>
--
73
-Jim
NU0C
|
Based on what Mr. Google is showing me they are axial ceramic capacitors. I'm thinking now that the pink ones are also. That would explain the schematic discrepancies. I don't think I have ever heard of any failing. 73 -Jim NU0C On Fri, 02 Feb 2024 09:32:15 -0800 "Rick K8EZB" <frboswell@...> wrote: Identifying RV75 capacitors:
The components in the photo below include both resistors and capacitors on the RV75 RF & Analog board, with the capacitors having the beige colored body and are designated on the ckt diag as C224, C225 etc. I am not familiar with this type of capacitor; a link to online info appreciated. The RV75 boards have many of this type of capacitor, the failure of which can cause much difficulty.
Thanks,
Rick
K8EZB
-- 73 -Jim NU0C
|
Identifying RV75 capacitors: The components in the photo below include both resistors and capacitors on the RV75 RF & Analog board, with the capacitors having the beige colored body and are designated on the ckt diag as C224, C225 etc. I am not familiar with this type of capacitor; a link to online info appreciated. The RV75 boards have many of this type of capacitor, the failure of which can cause much difficulty. Thanks, Rick K8EZB? 
|
You are absolutely right, Jim. I have never forgotten that warning.?
And that is just one of the? reasons I was shocked when I got the
combo shipment.
On 2/1/2024 7:34 PM, Jim Shorney wrote:
toggle quoted message
Show quoted text
This is not ham paranoia. Drake documentation EXPLICITLY STATES that the power supply must be removed from the speaker for shipment or damage will occur.
73
-Jim
NU0C
On Thu, 1 Feb 2024 18:33:34 -0500
"K4GM-George" <k4gm@...> wrote:
Listmates,
The precautions mentioned about shipping an AC-4 and an MS-4? should be
heeded.?? About 20 yrs ago a ham on the west coast shipped to me in
Virginia an AC-4 mounted inside of an MS-4.?? When I opened the box I
saw a bent up MS-4 barely holding on to an AC-4 by two screws.?? Ugh.??
I ended up getting my money back while keeping the shipment.? Converted
the AC-4 to an AC-4R and gave the MS-4 some time in the vice!
73, George K4GM
On 2/1/2024 4:54 PM, Jack N0JVR wrote:
Thanks for the info Richard!
On Thu, Feb 1, 2024 at 3:14?PM Richard Knoppow
<1oldlens1@...> wrote:
? IMPORTANT: If you sell this take the AC-4 out of the speaker box
and
pack it separately. If you ship it assembled it can break loose and
destroy the whole thing. Two separate boxes, one for the supply
and one
for the speaker. When you take the supply out of the box it will be
obvious if its had an update kit installed. There are two common kits
but one can also buy the caps from Hayseed Hamfest and replace them.
That will be less obvious.
On 2/1/2024 12:39 PM, Jack N0JVR wrote:
> I have an MS-4 w/AC4 power supply that I bought at a hamfest
last year
> with the intent of getting a Drake radio for it but since then my
> situation has changed and I'd be willing to part with it.? It's
in very
> good condition and I know the ham I bought it from and he
assured me
> that it worked.? I'm not sure if it's had the cap rebuild but if
there's
> a way I can tell it's been done let me know and I'll look at it.
> Thanks, Jack N0JVR
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
This is not ham paranoia. Drake documentation EXPLICITLY STATES that the power supply must be removed from the speaker for shipment or damage will occur. 73 -Jim NU0C On Thu, 1 Feb 2024 18:33:34 -0500 "K4GM-George" <k4gm@...> wrote: Listmates,
The precautions mentioned about shipping an AC-4 and an MS-4? should be
heeded.?? About 20 yrs ago a ham on the west coast shipped to me in
Virginia an AC-4 mounted inside of an MS-4.?? When I opened the box I
saw a bent up MS-4 barely holding on to an AC-4 by two screws.?? Ugh.??
I ended up getting my money back while keeping the shipment.? Converted
the AC-4 to an AC-4R and gave the MS-4 some time in the vice!
73, George K4GM
On 2/1/2024 4:54 PM, Jack N0JVR wrote:
Thanks for the info Richard!
On Thu, Feb 1, 2024 at 3:14?PM Richard Knoppow
<1oldlens1@...> wrote:
? IMPORTANT: If you sell this take the AC-4 out of the speaker box
and
pack it separately. If you ship it assembled it can break loose and
destroy the whole thing. Two separate boxes, one for the supply
and one
for the speaker. When you take the supply out of the box it will be
obvious if its had an update kit installed. There are two common kits
but one can also buy the caps from Hayseed Hamfest and replace them.
That will be less obvious.
On 2/1/2024 12:39 PM, Jack N0JVR wrote:
> I have an MS-4 w/AC4 power supply that I bought at a hamfest
last year
> with the intent of getting a Drake radio for it but since then my
> situation has changed and I'd be willing to part with it.? It's
in very
> good condition and I know the ham I bought it from and he
assured me
> that it worked.? I'm not sure if it's had the cap rebuild but if
there's
> a way I can tell it's been done let me know and I'll look at it.
> Thanks, Jack N0JVR
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
-- 73 -Jim NU0C
|
A follow-up to my previous post ¡°RV75 Issues:¡± Current status following additional trouble shooting time:
?? Burned 150 ohm resistor (R218) in PTO ENABLE line on RF & Analog board: so far no cause of resistor damage apparent. The only DC path through this resistor showing on my manual ckt diag is from the TR7 ENABLE line via the PIN diode and to the TR7 RV7 connector via P207.
?? When I connect an RV7 to the TR7, the RV7 works as expected suggesting that the PTO switching circuits are working normally in the TR7, and that my problem is likely contained to the RV75.
?? Using an in-ckt test instrument, the capacitance value and ESR value for each electrolytic on both boards is fairly close to the labeled value for capacitance and fairly close to the published ¡°typical¡± ESR values ?for aluminum electrolytics taking into account capacitance and voltage. My current thinking is that none of the ESR values are outliers to the extent that there is an obvious problem with the capacitor. I will change all of these caps on Jim¡¯s recommendation but currently doubt that these are linked to the burned resistor.
?? Damaged 10K resistor (no R2xx designation, not shown on my ckt diag): The damage appears to be of a mechanical nature, and not due to heating. ??This is in a part of the ckt that does not appear to be associated with the burned resistor. ?How such damage might have occurred is a mystery. This RV75 was in Ron Baker¡¯s shop in 2015 and got a clean bill of health.
?? My best thinking at the moment is that the evidence points (weakly) to the PIN diode as far as the burned resistor is concerned. I have new ones on the way and will change this out.?
?? There may be other problems than the burned and broken resistors and we will sort these out one step at a time.
Any informed insights most welcome as I am seeing this for the first time ever.
Thanks,
Rick
K8EZB
?
|
Interesting discussion......!
While I don't recommend shipping an AC-4 inside?an MS-4, it can be done with reduced risk successfully.? I proved that 25 years ago with one shipped that way to a ham in France.
Whenever I ship a 4 line (or 7-line), the item either gets the feet removed, bagged and placed somewhere safe within the item, or it is placed on at least a? 1" thick piece of pink high density styrofoam with holes cut out to match the feet such that the entire bottom surface of the "box" rest on that HD stryrofoam.? The AC-4 was installed in the MS-4 with its usual screws, and "blocked" tightly on the three inner open sides with many layers of cardboard (not corrugated?cardboard!).? That whole assembly then was wrapped tightly with multiple?layers?of bubble wrap and taped up.? It was placed in a box with 2" of that pink HD styrofoam insulation cut to fit tightly around the bubble wrapped item.? Box was 3 ply heavy duty.? The idea is to have nothing?able to move inside the box and to protect the inner item from damage should it be whacked externally.
I'll admit this was a long time ago and I am not sure that our postal/delivery systems are as radio friendly as they once were.? Most things I ship now are double boxed and a layer of at least 1" of that pink HD styrofoam goes between the inner and outer box.? I often use corner protectors...plastic, or heavy?corrugated?cardboard... as well.
And I still have trouble sleeping nights?until I get word the item arrived safely!
YMMV! 73 Peter VE7PS
On Thu, Feb 1, 2024 at 3:33?PM K4GM-George < k4gm@...> wrote:
Listmates,
The precautions mentioned about shipping an AC-4 and an MS-4? should
be heeded.?? About 20 yrs ago a ham on the west coast shipped to me
in Virginia an AC-4 mounted inside of an MS-4.?? When I opened the
box I saw a bent up MS-4 barely holding on to an AC-4 by two
screws.?? Ugh.?? I ended up getting my money back while keeping the
shipment.? Converted the AC-4 to an AC-4R and gave the MS-4 some
time in the vice!??
73, George K4GM
On 2/1/2024 4:54 PM, Jack N0JVR wrote:
Thanks for the info
Richard!
On Thu, Feb 1, 2024 at 3:14?PM
Richard Knoppow < 1oldlens1@...>
wrote:
?
? IMPORTANT: If you sell this take the AC-4 out of the speaker
box and
pack it separately. If you ship it assembled it can break
loose and
destroy the whole thing. Two separate boxes, one for the
supply and one
for the speaker. When you take the supply out of the box it
will be
obvious if its had an update kit installed. There are two
common kits
but one can also buy the caps from Hayseed Hamfest and replace
them.
That will be less obvious.
On 2/1/2024 12:39 PM, Jack N0JVR wrote:
> I have an MS-4 w/AC4 power supply that I bought at a
hamfest last year
> with the intent of getting a Drake radio for it but since
then my
> situation has changed and I'd be willing to part with
it.? It's in very
> good condition and I know the ham I bought it from and he
assured me
> that it worked.? I'm not sure if it's had the cap rebuild
but if there's
> a way I can tell it's been done let me know and I'll look
at it.?
> Thanks, Jack N0JVR
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
Jerry:
Correct......the load control is always adjusting the LOAD cap as it is rotated, regardless of whether it's pushed in or not.? Pushing it in just disconnects the meter as a Plate Current Meter and connects it as a Relative Output Meter.
So are you seeing RF Output on the internal meter with the LOAD control depressed now?
R13A is actually part of the Plate Current metering circuit, not the relative Output circuit.? I may have misled you on that earlier.
So...to tune the PA you do not need to push in on the LOAD control at all while you watch an external RF Output meter connected to the output of the PA.? Typically you start off with the load control at about 10 o'clock or a bit less, and TUNE for a plate current dip, with reduced TX Gain.? Increase gain a bit at a time, dip again and rotate the LOAD control clockwise slightly.? RF output should?go up slightly.? Gradually increase the tx gain, dipping the plate current, and increase LOAD slightly until you kind of max out on all 3 controls.? This is harder to explain?that it is in real?life!? Once you get used to it, you can do all of it in about 20 seconds.? On the XCVR's?(with 3 good PA tubes), you should see 150+ watts (or even more) on 75m, dropping to maybe 100w or so on 10m.
If the Plate Current dip does not coincide with a peak in output...and you are using a known good 50 ohm load.... yes, neutralization should be checked.? I don't like the method described in the Drake manuals, and have had much better success by disconnecting the SCREEN voltage, putting a coaxial?TEE in the output?line with one lead going to the dummy load and the other going to an oscilloscope...BUT ONLY connect the scope AFTER you have tuned up on 10m with?screen voltage still connected.? ONLY connect the scope to the TEE AFTER you have disconnected the screen voltage.? Screen voltage is easily disconnected at the feedthrough capacitor where it passes through a shield to the 68 ohm screen resistors under the PA cage.? Make sure you prevent your disconnected lead from shorting out.? Make sure power is off when you do this and bleed off the?+700V line too! Or better yet...just disconnect the AC-4!? Don't touch the tuning controls - they should remain where you were tuned up on 10m.
If you see Plate Current jumping around while tuning up on 10m, you may have to neutralize on 15m after tuning up there first.? Unplug the AC-4 at the xcvr, disconnect screen voltage, plug in the AC4 and power up again, connect the scope to the tee and adjust the neutralization cap with an insulated screwdriver for a minimum output shown on the scope.? Then shut down, unplug the AC-4 supply at the xcvr, reconnect the screen voltage wire, apply power again, tune up on 10m (scope disconnected!), then power down/disconnect the AC-4, re-disconnect screen voltage, connect the scope again and repeat on 10m for a minimum.
If you are uncomfortable messing about with HV, get some help or have someone who is, do it for you.? You don't want to blow up your scope, or worse yet....get yourself zapped with either the 300V screen voltage or especially the 700V HV!
Once you get used to doing this way, you'll never use the neutralization method in the Drake manual.? Kenwood made this easy for us with their hybrid tx and xcvr's by putting in an SG switch (screen grid) which allowed you to disconnect the screen voltage with the flick of a switch on the rear panels.? It was meant for transverter use, to provide minimal drive to a VHF transverter, but sure makes neutralization with a scope easy!
Safety FIRST!? Be very careful!? Take each step slowly and make sure that any time you are sticking your hands in the bottom of the radio that the AC-4 is off and is disconnected at the xcvr.
73 Peter VE7PS
On Thu, Feb 1, 2024 at 3:00?PM Jerry NY2KW < josternmd@...> wrote: Hi Peter,
Thanks for these great tips.? Can you help me understand how the Load slide function knob works?? Am I correct that is doesn't matter if pushed in or not, the Load knob remains mechanically linked to C95 capacitor and this loading cap is being moved same way regardless of whether knob is pushed in or not?? So I should be able to tune without pushing it in by only using my external wattmeter and the plate current?? ?I think something else is off though as peak output is not coinciding with plate dip... I guess that's part of a neutralization issue?
73 Jerry NY2KW
|
Listmates,
The precautions mentioned about shipping an AC-4 and an MS-4? should
be heeded.?? About 20 yrs ago a ham on the west coast shipped to me
in Virginia an AC-4 mounted inside of an MS-4.?? When I opened the
box I saw a bent up MS-4 barely holding on to an AC-4 by two
screws.?? Ugh.?? I ended up getting my money back while keeping the
shipment.? Converted the AC-4 to an AC-4R and gave the MS-4 some
time in the vice!??
73, George K4GM
On 2/1/2024 4:54 PM, Jack N0JVR wrote:
toggle quoted message
Show quoted text
Thanks for the info
Richard!
On Thu, Feb 1, 2024 at 3:14?PM
Richard Knoppow < 1oldlens1@...>
wrote:
?
? IMPORTANT: If you sell this take the AC-4 out of the speaker
box and
pack it separately. If you ship it assembled it can break
loose and
destroy the whole thing. Two separate boxes, one for the
supply and one
for the speaker. When you take the supply out of the box it
will be
obvious if its had an update kit installed. There are two
common kits
but one can also buy the caps from Hayseed Hamfest and replace
them.
That will be less obvious.
On 2/1/2024 12:39 PM, Jack N0JVR wrote:
> I have an MS-4 w/AC4 power supply that I bought at a
hamfest last year
> with the intent of getting a Drake radio for it but since
then my
> situation has changed and I'd be willing to part with
it.? It's in very
> good condition and I know the ham I bought it from and he
assured me
> that it worked.? I'm not sure if it's had the cap rebuild
but if there's
> a way I can tell it's been done let me know and I'll look
at it.?
> Thanks, Jack N0JVR
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
Hi Peter,
Thanks for these great tips.? Can you help me understand how the Load slide function knob works?? Am I correct that is doesn't matter if pushed in or not, the Load knob remains mechanically linked to C95 capacitor and this loading cap is being moved same way regardless of whether knob is pushed in or not?? So I should be able to tune without pushing it in by only using my external wattmeter and the plate current?? ?I think something else is off though as peak output is not coinciding with plate dip... I guess that's part of a neutralization issue?
73 Jerry NY2KW
|
Re: TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
Jerry:
Yes - the slide switch just switches between Plate Current and Relative?Output Power.? Rotating the LOAD control changes the loading cap and will result in a change in output....likely lower, if you have already dipped and loaded for max output on your external meter.
I tend to ALWAYS use an external?output meter for tuning and avoid using the internal RF Output meter.? Of course I DO use the meter in Plate Current mode!
Keeping that switch clean is really important, especially as I have seen it prevent seeing ANY Plate Current when trying to set the bias as a 1st step. Cleaning it is always part of any routine pre-operational check up on a new-to-me tx/xcvr.
73 and GL!
Peter VE7PS
On Thu, Feb 1, 2024 at 2:02?PM Jerry NY2KW < josternmd@...> wrote: Hi Peter,
I will clean the slide switch and report back.? I have to look at the schematic but does the slide switch only affect meter circuit?? Shouldn't I be able to increase the output on the wattmeter (LP-500) while rotating the pushed in knob despite the absence of any meter reading?
|
Re: TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
Hi Peter,
I will clean the slide switch and report back.? I have to look at the schematic but does the slide switch only affect meter circuit?? Shouldn't I be able to increase the output on the wattmeter (LP-500) while rotating the pushed in knob despite the absence of any meter reading?
|
Gentlemen, Be sure to heed the warning to remove the power supply and ship separately.? Handling during shipping WILL cause the rear corners to collapse and fold.? If that hasn't happened over the years, consider yourself lucky.? It's just cosmetic and not really visible from the front, but mind as well do everything you can to keep it pristine :?-?)
On Thu, Feb 1, 2024, 15:56 Ronnie Hull - W5SUM < w5sum@...> wrote: Thanks sir! ? I have an MS-4 w/AC4 power supply that I bought at a hamfest last year with the intent of getting a Drake radio for it but since then my situation has changed and I'd be willing to part with it.? It's in very good condition and I know the ham I bought it from and he assured me that it worked.? I'm not sure if it's had the cap rebuild but if there's a way I can tell it's been done let me know and I'll look at it.? Thanks, Jack N0JVR
George I¡¯m looking for an AC4 I¡¯m ok with something that needs a capacitor rebuild? Regards Tim KD2SC?
On Thursday, February 1, 2024 at 03:12:30 PM EST, K4GM-George < k4gm@...> wrote:
Ron,
I think I have what you want. A few months ago I? moved to a new QTH
and am still in the process of unboxing "shelf" gear.??? I'll dig
into my MS-4/AC-4 boxes and will let you know.?? I'll send you a
picture and then you make an offer.
73, George K4GM
On 2/1/2024 2:51 PM, Ronnie Hull -
W5SUM wrote:
Anyone have a MS4 they will part with reasonably?
Does not have to be pretty but has to be complete and work.
Thanks
Ron W5sum?
|
Thanks for the info Richard!
On Thu, Feb 1, 2024 at 3:14?PM Richard Knoppow < 1oldlens1@...> wrote: ? ? IMPORTANT: If you sell this take the AC-4 out of the speaker box and
pack it separately. If you ship it assembled it can break loose and
destroy the whole thing. Two separate boxes, one for the supply and one
for the speaker. When you take the supply out of the box it will be
obvious if its had an update kit installed. There are two common kits
but one can also buy the caps from Hayseed Hamfest and replace them.
That will be less obvious.
On 2/1/2024 12:39 PM, Jack N0JVR wrote:
> I have an MS-4 w/AC4 power supply that I bought at a hamfest last year
> with the intent of getting a Drake radio for it but since then my
> situation has changed and I'd be willing to part with it.? It's in very
> good condition and I know the ham I bought it from and he assured me
> that it worked.? I'm not sure if it's had the cap rebuild but if there's
> a way I can tell it's been done let me know and I'll look at it.?
> Thanks, Jack N0JVR
>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Re: TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
Jerry:
Common issue....clean the slide switch behind the front?panel on the LOADING control shaft.? If dirty, it can affect both Plate Current and Output readings.? Spray some De-Oxit D5 into the switch and work it a bunch of times.? That should clear up the problem.? Also check the resistor on the slide switch (R13A) to make sure it isn't missing?or burned up.? Value is selected during production.
To me....your LOAD control is behaving?normally.? You are just not seeing?the RF being picked up and sent to the TR-4C meter.
73 Peter VE7PS
On Thu, Feb 1, 2024 at 1:36?PM Jerry NY2KW < josternmd@...> wrote: I am a Drake newbie and have a TR-4C that was gone over by an expert and working well prior to shipping.
Here's what I am seeing when tuning up at 3.6 MHz:
?
?
- I begin with Load and Xmtr gain knobs at zero (fully counter-clockwise) and ?then peak audio with RF Tune
- Set mode to X-CW and Sideband X and Idle bias is 0.1 on plate meter
- I increase Xmtr gain until meter reads about 0.2 and dip meter current with Plate knob ?
- Next I peak plate current with RF Tune knob and re-dip plate current.
- At this point with the Xmtr gain set to give me 0.2 A and plate dipped, I get around 40W
- I increase Xmtr gain until plate current max¡¯s out at around 0.35 ¨C 0.4, and re-dip Plate which gives me output of 135W.
- When I push in Load knob (Rel_Output) the meter drops to zero but wattmeter still reading about 135W.?
At this point, with the Load knob pushed all the way in, if I rotate the knob clockwise power start dropping down from 135 to about 100W with knob pushed in and I stopped around mid-way.?
?
Once I release the knob, meter current is back again.? If I try to increase Load knob (not pushed in) slowly while re-dipping plate current, output drops progressively.
?
I assume I¡¯m not seeing maximum output because the pushed-in Load knob is either mechanically or electrically broken and therefore not matching the PA finals to the 50 ohm load.
Any advice how to repair this or further diagnose the problem?
Jerry NY2KW
? ??
|
Re: TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
Your analysis makes sense. I assume you have an external power meter of some sort. Can you take the cover off the unit and inspect what is happening with the Load/Relative Power knob? With power off of course. if there is a mechanical problem it should be visible. I don't have a TR-4C and it is enough different from the TR-4 (which I do have) so that my idea may not be valid.
toggle quoted message
Show quoted text
On 2/1/2024 1:36 PM, Jerry NY2KW wrote: I am a Drake newbie and have a TR-4C that was gone over by an expert and working well prior to shipping.
Here's what I am seeing when tuning up at 3.6 MHz:
1. I begin with Load and Xmtr gain knobs at zero (fully
counter-clockwise) and ?then peak audio with RF Tune
2. Set mode to X-CW and Sideband X and Idle bias is 0.1 on plate meter
3. I increase Xmtr gain until meter reads about 0.2 and dip meter
current with Plate knob
4. Next I peak plate current with RF Tune knob and re-dip plate current.
5. At this point with the Xmtr gain set to give me 0.2 A and plate
dipped, I get around 40W
6. I increase Xmtr gain until plate current max¡¯s out at around 0.35 ¨C
0.4, and re-dip Plate which gives me output of 135W.
7. When I push in Load knob (Rel_Output) the meter drops to zero but
wattmeter still reading about 135W.
At this point, with the Load knob pushed all the way in, if I rotate the knob clockwise power start dropping down from 135 to about 100W with knob pushed in and I stopped around mid-way.
Once I release the knob, meter current is back again.? If I try to increase Load knob (not pushed in) slowly while re-dipping plate current, output drops progressively.
I assume I¡¯m not seeing maximum output because the pushed-in Load knob is either mechanically or electrically broken and therefore not matching the PA finals to the 50 ohm load.
Any advice how to repair this or further diagnose the problem?
Jerry NY2KW
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
TR-4C "Rel_Out" Knob (Load pushed in) Not Working Correctly
I am a Drake newbie and have a TR-4C that was gone over by an expert and working well prior to shipping. Here's what I am seeing when tuning up at 3.6 MHz:
?
?
- I begin with Load and Xmtr gain knobs at zero (fully counter-clockwise) and ?then peak audio with RF Tune
- Set mode to X-CW and Sideband X and Idle bias is 0.1 on plate meter
- I increase Xmtr gain until meter reads about 0.2 and dip meter current with Plate knob ?
- Next I peak plate current with RF Tune knob and re-dip plate current.
- At this point with the Xmtr gain set to give me 0.2 A and plate dipped, I get around 40W
- I increase Xmtr gain until plate current max¡¯s out at around 0.35 ¨C 0.4, and re-dip Plate which gives me output of 135W.
- When I push in Load knob (Rel_Output) the meter drops to zero but wattmeter still reading about 135W.?
At this point, with the Load knob pushed all the way in, if I rotate the knob clockwise power start dropping down from 135 to about 100W with knob pushed in and I stopped around mid-way.?
?
Once I release the knob, meter current is back again.? If I try to increase Load knob (not pushed in) slowly while re-dipping plate current, output drops progressively.
?
I assume I¡¯m not seeing maximum output because the pushed-in Load knob is either mechanically or electrically broken and therefore not matching the PA finals to the 50 ohm load.
Any advice how to repair this or further diagnose the problem?
Jerry NY2KW
|
Re: One last call for Help..T-4XB
Keep in mind that the side tone comes up the anti-VOX line from the transmitter. The Anti-VOX gain is also the side tone gain. Its usual for it to require a different setting for CW than for SSB. I don't know what would result in oscillation there but the problem is probably in the transmitter. The side tone comes from the same oscillator arrangement that is used to generate the TUNE tone, it is the mic pre-amp with a feed back phase shift network.
Is your feed through with key up the same frequency as the side tone (you probably said already)? That might be a clue as to where its coming from.
In general all the VOX adjustments are differernt for CW and SSB. A bit of a PITA but all things considered one can get used to it.
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On 2/1/2024 11:20 AM, Steve Johnston via groups.io wrote: I don't have the schematic here, but sometimes when I've had audio bleeding onto circuits where it did not belong, I found that the power line into the audio source stage had a bypass capacitor fail (go low in value with age).? It was letting audio ride on the B+ power backwards out of the audio source stage.? The audio was then able to get into another stage and be heard there (bypassing whatever was the normal switching or muting scheme).
73?? Steve? WD8DAS
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Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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IMPORTANT: If you sell this take the AC-4 out of the speaker box and pack it separately. If you ship it assembled it can break loose and destroy the whole thing. Two separate boxes, one for the supply and one for the speaker. When you take the supply out of the box it will be obvious if its had an update kit installed. There are two common kits but one can also buy the caps from Hayseed Hamfest and replace them. That will be less obvious.
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On 2/1/2024 12:39 PM, Jack N0JVR wrote: I have an MS-4 w/AC4 power supply that I bought at a hamfest last year with the intent of getting a Drake radio for it but since then my situation has changed and I'd be willing to part with it.? It's in very good condition and I know the ham I bought it from and he assured me that it worked.? I'm not sure if it's had the cap rebuild but if there's a way I can tell it's been done let me know and I'll look at it. Thanks, Jack N0JVR
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Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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On Feb 1, 2024, at 2:39?PM, Jack N0JVR <jackr9617@...> wrote:
? I have an MS-4 w/AC4 power supply that I bought at a hamfest last year with the intent of getting a Drake radio for it but since then my situation has changed and I'd be willing to part with it.? It's in very good condition and I know the ham I bought it from and he assured me that it worked.? I'm not sure if it's had the cap rebuild but if there's a way I can tell it's been done let me know and I'll look at it.? Thanks, Jack N0JVR
George I¡¯m looking for an AC4 I¡¯m ok with something that needs a capacitor rebuild? Regards Tim KD2SC?
On Thursday, February 1, 2024 at 03:12:30 PM EST, K4GM-George < k4gm@...> wrote:
Ron,
I think I have what you want. A few months ago I? moved to a new QTH
and am still in the process of unboxing "shelf" gear.??? I'll dig
into my MS-4/AC-4 boxes and will let you know.?? I'll send you a
picture and then you make an offer.
73, George K4GM
On 2/1/2024 2:51 PM, Ronnie Hull -
W5SUM wrote:
Anyone have a MS4 they will part with reasonably?
Does not have to be pretty but has to be complete and work.
Thanks
Ron W5sum?
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Jim Shorney
K4GM-George
Ronnie Hull - W5SUM