1st build, need a little help

DFMoore · Post by **DFMoore** » Sun Jan 01, 2012 12:23 am

Your correct it is a 47 ohm.

cbass · Post by **cbass** » Sun Jan 01, 2012 12:29 am

The way you have The preamp tube wired is reverseof RJ's layout.Won't matter as long as you wire it right.

So pin 3 should go directley to the 1k5 then to ground.

pin 8 should goto the 1k5 then through the 47ohm to ground.

Make sure you have the negative end of your bypass caps towards ground.

DFMoore · Post by **DFMoore** » Sun Jan 01, 2012 12:50 am

AH! I think you found my problem. I have pin 3 going to a 47ohm not a 1k5. Do you think that could cause my issue?

Many Thanks,

cbass · Post by **cbass** » Sun Jan 01, 2012 1:08 am

yes that would be a problem I can't see the value on your pic.But that would definatley cause the the 0 volts at pin 3

ampgeek · Post by **ampgeek** » Sun Jan 01, 2012 1:09 am

If the 47 ohm was going directly to ground...probably.

If the 1k5 was between it and ground...probably not.

Lift the negative feedback wire from the output jack and measure resistance from pin 3 to ground.

Good luck,
Dave O.

DFMoore · Post by **DFMoore** » Sun Jan 01, 2012 1:10 am

Good News and Bad News. I replaced the 47 Ohm with the correct 1K5. I now have 1.29 volts at pin #3. The bad news is I still have the same very low distorted volume.

cbass · Post by **cbass** » Sun Jan 01, 2012 1:14 am

Well that sucks.

Post a pic of your input jack wiring

cbass · Post by **cbass** » Sun Jan 01, 2012 1:16 am

Just a little tip I like to measure my resistors with a meter.Those color bands can be hard to read.
Especially if your like me.Blind in one eye.Can't see very good out of the other

DFMoore · Post by **DFMoore** » Sun Jan 01, 2012 1:26 am

I have been a little suspect of the input jack. I've rewired it a few times, the reason for all of the solder. The Red wire leads to a 68K resister then to pin #2. The Green wire leads to ground. The resister is a 1 Meg.

cbass · Post by **cbass** » Sun Jan 01, 2012 1:42 am

hmm looks right.

Chack all your connections to ground with your meter.

Make sure your not looking over anything obvious.Bad cord.Bad speaker guitar volume down etc.

DFMoore · Post by **DFMoore** » Sun Jan 01, 2012 11:43 am

OK, I have checked all the grounds, the speaker, the cable, the guitar volume and all is ok. Please look over my output jack. The blue wire leads to a 22K resister. Also what is the directional pwr flow for the 10uf cap that is with the 1K5 (center left of layout)?

Oh yea, Thanks for all of your help.

cbass · Post by **cbass** » Sun Jan 01, 2012 3:58 pm

Looks right.Make sure the nfb (blue wirw)Is connected to the tip and not the sleeve.

You might try reflowing some solder joints.

The negative end of tht 10uf cap should be conected to the 22k 47ohm junction

DFMoore · Post by **DFMoore** » Sun Jan 01, 2012 5:46 pm

OK, Blue wire is correct and cap is in the correct direction. I cleaned up the ugly solder joints and put in a 6V6 tube I know is good. NO change in volume.

How about the .02uF caps? I don't see a pos or neg on either end. Are these polar?

RJ Guitars · Post by **RJ Guitars** » Sun Jan 01, 2012 11:17 pm

Dave,

You've found the planets best collection of guys offering tube amp tech support... and some generally decent guys.

You're getting pretty close to the answer now. Looking at the input and output jack is a great place to start. The self shorting jacks prevent you from accidentally operating without a load on the output when you don't have a speaker hooked up and also for silencing random noise when you don't have a cord plugged into the amp input. They can snag you up and kill your signal going in or out until you have them right though so it's a good practice to look at them early in the debugging process.

You said you get a buzz (sonic buzz I hope) when you touch certain terminals. This is telling you that you have signal going through the circuit. That gives you some hope that you have a lot of stuff in the right place doing the right thing. Can you post the schematic with your voltages labeled on it? this will tell us a lot more about what your amp is doing.

I've got plenty of stock on those preamp tubes but it's not clear yet that we've looked at everything. Tubes are pretty tough unless you really abuse them... hopefully we can make it work with what you have there.

thanks,

rj

DFMoore · Post by **DFMoore** » Mon Jan 02, 2012 12:15 am

See attached pic with voltage readings.

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