Metropoulos Forum

Hi, I am building a JTM45 kit and right now I am testing the voltages on the preamp.

V1 voltages read Pin 1- 213.6
Pin 3- 1.7
Pin 6- 221
Pin 8- 1.7

V2 voltages read Pin 1- 183
Pin 3- 1.1
Pin 6- 315
Pin 8- 186

V3 voltages read Pin 1- 378 (which is extremely high)
Pin 3- 6.1 (Extremely low)
Pin 6- 378 (High)
Pin 8- 6.1 (Low again)

Does anybody out there have any idea on what is wrong?

Are you able to post some gutshots??

I don't have time right now, but I pulled out the board to check my connections. I thought I might of had a bad 470k resistor but 100% positive. Any ideas what to look for before I solder the tube sockets back in to make sure I am not missing anything? Everything looks good to me. Went back over the instructions and nothing seems to me out of place. Thanks, I'll post a picture as soon as I can tomorrow.

TUbes in?

Yes tubes were in. My last should have said NOT 100% positive. I will check back Tomorrow, I'm off to work now. EEERRRRRRR! I'll have my son keep an eye on these post. Thank you people.

zrAC/DC wrote: I thought I might of had a bad 470k resistor but 100% positive.

There is no 470K resistor in a JTM45. A common mistake though is for guys to put a 470K instead of a 470 ohm on the PI (V3) cathode. This causes high plate voltages, low cathode voltages on V3, and weak output. So check that resistor (follow wire on V3 pins 3/8 straight to it), be sure it is a 470 ohm, not 470K.

Thats IT! My son told me he figured it out, then said hey, someone pointed it out on the forums. (Wise ass) Amp is up and running! Thanks for the help!

Sounds really good, I can't see how it can get better

Thanks Steve!

Same thing (470Kohm vs 470ohm) had me pulling my hair out on my '68 build for 3 hours tonight.

Kind of wish I would of searched the forum a lot sooner for the problem. This thread was like the 3rd on the list.