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109.9

Well there you have it.... almost 10% low?!! That pretty much covers all the low voltage conditions. About 10% low?!
Is there any where you can plug her in that's closer to 117/120?
Stew

That means you only have 5.2V in your heaters, assuming you've measured with your meter set correctly this time. If you run your amp with the heater voltage more than 10% above or below the rated 6.3V AC, the lifetime of your tubes will suffer, particularly the rectifier and power tubes. So your heaters should never be run below 5.7V AC or above 6.9V AC.

+1

Or failing that you can artificially boost the AC voltage coming into the amp by means of a "Vintage Voltage Adapter". These are usually used to reduce the incoming AC voltage, but if you swap the auxiliary transformer's secondary connections around, it will instead boost the AC voltage coming into your amp.

www.geofex.com/Article_Folders/vintvolt/vintvolt.htm

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Could this cause the amp to squeal with the gain turned all the way up?

It's remotely possible, not very likely.

I think already covered the squeal issue with someone recently. Was that you, or someone else? I'm suffering badly from sleep deprivation at the moment, and my brain feels all messed up....

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You can do a search and find a few threads on the topic. But basicly you want to get a chopstick or similar non-conductive probe and try moving around the wires inside the amp/. I think the shielded cables from the i/p jacks and the one from the gain pot are the culprits.
Stew

OK, had a short nap and now I feel a little better. I've found my other recent post, which it turns out was in reply to plexiblues.

Apart from that, like I said before, you need to boost your AC voltage coming into the amp, so that your tubes don't suffer, and also so your amp starts to sound as it's meant to.

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I have tried everything. I cant figure out what to do when it starts squealing.

Then I suggest you post some good clear pictures for the folks here to take a look at. They may spot something you haven't noticed.

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Jeez
Come down Phil
Dude, if you could possibly, send some shots of what you've built then we could look and help determine, well, what's up !

Plus we love to look!!!
Damn peeping toms
So common' send it

Cheers

littlejac

I'm always happy to look at gut shots, but I don't have all the answers either. So I like reading entrails to be a group effort where, you, me and everyone gets a chance to win the fault-spotting contest.

Plus being somewhat colour-blind doesn't help me. I can't read resistor colour bands, and for instance, I also find it hard at times to distinguish between green wire and purple wire. That's why the Triwatt prototype ended up with some of the ground connections being done in purple. Quite a few times I've been asked why I chose a to have a career in electronics.

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I would really appreciate it if you guys would take a look.

Thanks in advance,
Jon

http://s652.photobucket.com/albums/uu241/jcr1234/

So far we've:
- twisted the OT wires
- Reversed OT leads
- swapped tubes
- chopstick leads (its a combo so very short leads)
- checked grounds for continuity
- confirmed resistor values around V2 and PI.
- measured voltages are low but main is 110.
- PI voltages are quite low. B+ is low. Using NOS rectifer. It
could be bad.
- used our regular coax from gain to V2 pin 2. Confirm it is grounded at control end. It goes under board. I put it on top FWIW..

I've looked at pics and it looks decent with correct parts on board.

Can we get the voltages up? Shorten coax? Go direct across top of board?

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

Hmmm...before we get all crazy (too late maybe? ) , has the amp been running with the bottom of the chassis open & unshielded? I've found that once you close it up & shield it you can get rid of some squealing issues. Environment can impact it too. I sometimes have a perfectly running build on my bench, but once it gets upstairs around all the other electronic gear I will get squealing without shielding the bottom of the chassis.

I thought I had mentioned that in this thread, but it might have been a different one. Faulty wiring in my head sometimes...

Good thought. Mavbe a BFO - Blinding Flash of the Obvious

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

as much as I wish the BFO was the answer, sadly, it does the same thing whether the back is open or closed and in any room of the house.

So, lets see if we can get the voltage up there. I doubt it will make the difference but it's another place to start.

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

didn't know you we're color-blind or I forget during the last barrage of meds
Must suck when looking at photos, colors always help

Further Recommendations in order of execution:

Get the voltage issue fixed.

Check grounds with ohm meter (should be less that 1 ohm) . Some continuity meters or checkers will often show a connection as OK when it actually has some resistance. Check the solder joints on the ground connections. Reheat/touch up.

Move the shielded wire from Gain control to V2 to above the board and shorten it. In some extreme cases all the gain AND volume controls may need to be connected using shielded wire.
Note: Phil recommends using screened cable for all volume/gain controls with any amp showing squealing problems - not just extreme cases.

In some instances, the amps OT secondary ground is critical. Try a jumper from ground on the output jack to the ground lug. In the 18 or 15 the layout doesn’t ground the output -ve jack & I have had no problems.
Note: Phil recommends grounding the OT secondary in the case of TMB amps, especially if they have squealing problems - not just in extreme cases. I've seen that cure squealing problems a number of times.

Check the solder joints on all the filter caps. Reheat/touch up.

Richie Hall sometimes recommends twisting the wires connecting the PI output to the power tubes.

Try placing a film cap (eg Mallory 150) across each filter cap. [caps could be 0.1uF or 0.68uF]

Try 47pF or 100pF cap across the PI anodes.

Stephen & Phil

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