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PostPosted: Mon Feb 15, 2021 6:22 pm 
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I have checked over my build, corrected errors and still have not got working as yet. These are the latest voltages

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I am not sure about the V1 and V2 pin2 readings. I don't think there should be anything there and maybe I forgot to erase them from a previous read. In any case, the amp is hooked to a speaker and I can hear sounds when testing. Does anything look obviously wrong in the pic, aside from a few solder joints ?

Image
When I turn the amp off, I hear it power down thru the speaker. I have tested for continuity at all connections, but am still searching for an answer.

Any constructive help would be welcome, Thanks in advance, Mike


Last edited by mefgames on Thu Feb 18, 2021 4:28 pm, edited 2 times in total.

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PostPosted: Tue Feb 16, 2021 3:47 am 
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Hi Mike,

Two things I noticed at first glance: the number of poor solder joints and the weird resistor on V5. I've added some red arrows to the joints that immediately jumped out as needing work:

Image

You'll also see a purple arrow pointing to the grid stopper resistor on V5. It looks tiny and it looks discolored... has it burned out? It looks like it's not the correct wattage because it's so small.

I recommend remaking the solder joints I've highlighted with a good, powerful iron, with a good clean tip. Make sure to get them fully wet (i.e. all the solder melts in the joint) and don't starve them - several of the joints in your photo look like there simply isn't enough solder in them.

I see that the ground bus extends way past the presence control all the way to the power switch. I strongly recommend trimming that back to the presence pot away from the high voltage switches/wiring.

I don't think this will be the cause of a non-functioning amp, but your heater wires and your 5V yellow wires are too loose. I suggest tightening the twist on those to get them very tight. You're asking for hum right now!

But first I'd redo all those dry and starved solder joints along with the V5 resistor, then test again. Good luck!

-B


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PostPosted: Tue Feb 16, 2021 2:39 pm 
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bushwhacka wrote:
Hi Mike,

Two things I noticed at first glance: the number of poor solder joints and the weird resistor on V5. I've added some red arrows to the joints that immediately jumped out as needing work:

I will be re-flowing the joints today

Image

You'll also see a purple arrow pointing to the grid stopper resistor on V5. It looks tiny and it looks discolored... has it burned out? It looks like it's not the correct wattage because it's so small.

That resistor was missing in my kit, so I checked with Stephen and he said the 1/4 was would be okay. ps it's a shadow

I recommend remaking the solder joints I've highlighted with a good, powerful iron, with a good clean tip. Make sure to get them fully wet (i.e. all the solder melts in the joint) and don't starve them - several of the joints in your photo look like there simply isn't enough solder in them.

I see that the ground bus extends way past the presence control all the way to the power switch. I strongly recommend trimming that back to the presence pot away from the high voltage switches/wiring.

I don't think this will be the cause of a non-functioning amp, but your heater wires and your 5V yellow wires are too loose. I suggest tightening the twist on those to get them very tight. You're asking for hum right now!

But first I'd redo all those dry and starved solder joints along with the V5 resistor, then test again. Good luck!

-B


Thanks for the reply, Mike


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PostPosted: Tue Feb 16, 2021 5:42 pm 
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Voltages are quite off.
Good example, pin 2 of v2 should not have 70+ volts on it! Something is quite wrong there.
As already mentioned, there are many suspect. solder eyelets. Heat them up and fill them

Then Check your voltages at each of the power supply filters and report back.

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PostPosted: Tue Feb 16, 2021 8:55 pm 
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coco wrote:
Voltages are quite off.
Good example, pin 2 of v2 should not have 70+ volts on it! Something is quite wrong there.
V2 pin 2 did not have 70. I marked the wrong box and forgot to erase it


As already mentioned, there are many suspect. solder eyelets. Heat them up and fill them
I re-flowed all solder joints today


Then Check your voltages at each of the power supply filters and report back.

Reporting back with new voltages

Image
Thanks, Mike


Last edited by mefgames on Thu Feb 18, 2021 4:19 pm, edited 1 time in total.

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PostPosted: Wed Feb 17, 2021 12:13 am 
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Check the values of the resistors in the last two power supply nodes. Maa as jexsurecthey are wrll soldered in place.

Attachment:
9BCC635B-0756-4C57-8112-CBA8E4B104D5.jpeg
9BCC635B-0756-4C57-8112-CBA8E4B104D5.jpeg [ 503.26 KiB | Viewed 4206 times ]

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PostPosted: Wed Feb 17, 2021 11:21 am 
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19.9 and 2.0 left to right

I was so hoping you had found the problem. I just soldered them again, and the readings are the same.


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PostPosted: Wed Feb 17, 2021 2:39 pm 
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Are you getting any sound?

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PostPosted: Wed Feb 17, 2021 2:49 pm 
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There is a scratchy sound in some areas that comes thru the speaker when I'm testing


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PostPosted: Thu Feb 18, 2021 4:08 pm 
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Update, In checking and re-checking I found this 220k resistor( yellow arrow) was measuring 120k. I switched it out with another 220k that measured correctly, and the new one installed reads the same 120k now. It is connected to the relay board at the Com point(red arrow). ??? So, that's problem, but I don't know where to look next. Could that be the B rail low voltage problem, or is it something new and unrelated ?


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PostPosted: Thu Feb 18, 2021 9:25 pm 
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That value is affected by the trim pot so measuring in circuit is not reliable.

The PI pin 1 plate value is out of whack so check the value of the resistors and also the solder connections.
Get that right and we can move on.

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PostPosted: Fri Feb 19, 2021 2:01 am 
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What exactly does this mean, The PI pin 1 plate value ? I did re-solder all the connection points, checked for continuity, and re-measured voltages. Not much change. I am not a seasoned amp guru, but feel confident based on 4 previous amp builds that I am capable with some guidance.

Thank, Mike


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PostPosted: Fri Feb 19, 2021 8:51 am 
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It means The voltage on pin 1 is very low so either the tube is defective or the components in the chain are defective or the connections are suspect.
You need to eliminate each one.

This may help explain some things. See Amp Triage.

https://www.trinityamps.com/docs/Builde ... ooting.pdf

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PostPosted: Fri Feb 19, 2021 3:49 pm 
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Stephen is saying that pin 1 of V3 (the Phase Inverter-PI) has problems. If you look at the 12AX7 diagram pins 1 and 6 are the plate pins. Apologies if I over explained. :oops:

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PostPosted: Fri Feb 19, 2021 7:51 pm 
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Hankules wrote:
Stephen is saying that pin 1 of V3 (the Phase Inverter-PI) has problems. If you look at the 12AX7 diagram pins 1 and 6 are the plate pins. Apologies if I over explained. :oops:

Thanks, I welcome overexplaining. One can not learn too much.


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PostPosted: Tue Feb 23, 2021 2:34 pm 
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Update; I spent quite a bit of FaceTime with Coco yesterday in order to troubleshoot my build. He was beyond helpful, very patient, and walked me through steps to ascertain the problems I was having. Mostly re-doing my soldering and a continuity issue. I still have to go back and re-do some more things, but I have sound, albeit not full volume. Just wanted to let those that posted help and give a big thanks to Stephen. Hopefully, my next post will be to report full functionality.

Thanks, Mike


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PostPosted: Tue Feb 23, 2021 6:43 pm 
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Today I spent a good amount of time re-soldering those suspect connections in hopes that would do the trick, still wasn't getting much volume. While chopsticking around, specifically the volume pot, the volume level went right up. I also discovered I had not connected the jumper between the volume pot and the treble pot, so I installed that and re-soldered all connections to the volume pot. Sound level is where it should be, very little hum, if at all. Yay !!! Still have a few issues though,
1. the volume pot when turned all the way up, cuts out
2. not noticing much difference in the tone controls
3. One of the switches is not making much of a difference in tone, whereas the other when switched is very boomy
4. Presence knob has little or no effect
All in all, I am very happy and now that the big hurdle has been cleared, I'll be chasing down the smaller gremlins.

Mike


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