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You can't measure continuity through a cap so just check that all leads go where they are supposed to go. i.e. the wire/components are connected

The Normal channel looks wired up correctly, check that the lead from the .022cap /470K intersection turret, goes directly to the volume control. and the lead from the .01 on the board goes to the middle lead of the pot.

Check the pot value from one lug to the center lug. It should change as you rotate it.

Also, touch pin 7 with a small screwdriver and see if you get a noise/pop with the volume about 1/4 way up.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

QUOTE:
>> Also, touch pin 7 with a small screwdriver and see
>> if you get a noise/pop with the volume about 1/4 way up.

You mean pin 7 of V1?

Yes I mean V1.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Yes, I can touch pin seven with the volume up and get pops.

Are they pretty loud? If so, then it is probably in the connection from the input or the jacks.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Actually it wasn't loud. I assumed it would be louder. I did the test with vol at half max. I didn't mention that before because I'm not sure I can make an accurate judgment. With nothing plugged into the input I get very very weak speaker noise after 3/4 max vol. I get absolutely nothing with the cable plugged into the guitar.

I had a difficult time getting the inputs soldered to v1. I just couldn't work up the control and precision I felt I had at other areas. I really muddled through it. I did the normal low input resistor to pin 7 of V1 first. It was tough, I had the resistors terminal just into the solder joint with out good mechanical connection at all. The hi input was better connected but I still felt like I was working blind and couldn't really control the quality of the connections..

If I encountered any noise or nastyness at all I was prepared to rip out the input wiring and redo it (everything involving the Belkin shielded cable)...I sorta forgot about this when the plexi side worked so well and everything is nice and quite......

Maybe I should redo this next? Is there anything else to check first or another way to test?

Here is a pic of the current point of interest:

Test that the coax cable conductors didnt melt together inside. Do a continuity test with a jack plugged in and see .

Both channels the same problem - also check the connection at the tube pin and retouch the connections from the board at the pins for the normal channel

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Hey, Coco, I have been very busy with work but I finally took the time to troubleshoot my channel 1 problem.

First, I measured continuity through the instrument cable. If I plug into the normal hi input and clip a probe where the belkin shielded cable attaches to the solder tag at VI, and then touch the other probe to the instrument cable tip I get continuity. I do not get continuity if I touch the cable shield. If I then plug into any of the other amp inputs put stay clipped at this same point at the solder tag (the hi input for channel 1) I get no continuity for tip but I do for the shield. I can repeat this procedure with the same results for any and all the other inputs. That is, continuity from instrument cable tip to its appropriate input at V1. Changing the input that the instrument cable is plugged into abolishes continuity at the tip but gets continuity from cable shield. I wish I could explain it better but I have no experience with this stuff. However, it does appear that the shielded cable inputs to V1 are ok.

Now I have returned my attention back to the pots. Remember I told you that my normal channel pot measures 0 resistance and all the other pots measures their appropriate value when probing the two outer lugs. However it was sometimes hard to get stable readings and this seemed to be associated with how much stuff was soldered to a given lug. Therefore I redid the experiment with alligator clips and I took several measurements for each pot.

For each pot I clipped a probe to the two outer lugs and took readings with the pot at 0 and at 10. Then I repeated this with the rightmost clip now cliped to the wiper of the pot.

Here all my results:

MEASURING RESISTANCE ACROSS TWO OUTER LUGS

PLEXI CHANNEL
BASS (0) .496 (10) .275
MIDDLE (0) .025 (10) .024
TREBLE (0) .242 (10) .163
GAIN (0) .489 (10).085
VOLUME (0) .025 (10) .025

NORMAL CHANNEL
TONE (0).520 (10) .522
VOLUME (0) 0 (10) 0

For instance, with the BASS at O the reading across the two outer lugs was .496, approximate for the value of that pot, and it dropped to .275 as the pot was turned to (10). This trend occurred for all the other pots except for the 25k pots. They did not change much. I do not recall which pots were nonlinear. Interesting, for the normal input tone, the pots did approximately measure it 500k value but their was no drop. Most of the pots dropped to half their value. The NORMAL pot measured 0 at any setting.

MEASURING RESISTANCE BETWEEN OUTER LUG AND WIPER

PLEXI CHANNEL
BASS (0) 0 (10)272
MIDDLE (0) 0 (10) .025
TREBLE (0) 0 (10) .162
GAIN (0) .489 (10) .085
VOLUME (0) 0 (10) .025

NORMAL CHANNEL
TONE (0) 0 (10) .500
VOLUME (0) 0 (10) 0

For the PLEXI channel the results are as expected. The ranged from 0 to the approximate value at 10 as seen when measuring across the outer lugs. The TONE pot for the NORMAL channel measures fine but the VOLUME pot for the NORMAL channel does not behave like the other pots. It gave values of 0.0 except for around 8 where it measures approximately .100 but then immediately dropped to 0.

So you guys tell me. Is the volume pot bad? Is it due to something connected to the volume pot? Is this normal volume pot behavior? So far everything else with the amp seems to check out.

In regard to my last post with pot data let me stress that the pots were measured hooked up to everything else in circuit. A friend of mine who has built several amps tells me that the pot may not be bad. A lead may be shorting to ground and causing the pots failure. He didn't say to much more other than to truly test the pot I will have to remove everything connected to it. At this point I am more interested in looking for something that may be shorting out the pot than I am totally unhooking it.

Please let me know what you think? I am asking for ideas on what the problem may be.

That pot should have resistance across those lugs. You're going to have to take the parts off to really test it.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Do you agree that I am to the point on the trouble shooting of this silent channel to warrant removing all that is soldered to the pot and retest it.


If it tests ok, then should I just more carefully reassemble the connections to the pot?

Let me know if you can think of any more specific wire leads to test. I really like the idea that something maybe shorting the pot. If this were to be the case what would the most likely candidates be? We have covered several.

I am enjoying the plexi channel so much that I have been slow to move on this. This amp sounds great. Just awesome Marshall tone. What is so cool about the way the amp sounds now is that I have not really tubed it yet. I am just using randomly selected JJs. When I fine tune this amp it is probably going to sound much better.

Their was a bit of brittleness at high volume and gain that I corrected with a Evidence Audio Siren II speaker cable. The speaker cable I originally used was old and generic. The last time I heard a D chord with those high shrill overtones it was due to a cheap cable, this experience served me well as I didn't have to concern myself with tubes and looking within the amp for the culprit.

The wiring looks good.
Check to make sure the component leads soldered to the lugs aren't inadvertently touching ground.

If you have to take components off, check the resistance after each end is removed to see if it's a faulty component.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps