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?
Problem with voltages on V3
Moderator: VelvetGeorge
- zrAC/DC
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Problem with voltages on V3
~~Current Amps~~
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
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Re: Problem with voltages on V3
Are you able to post some gutshots??
Metroamp builds : 68` 50w (x2), 69` 100w, 68` 100w 12xxx (x3), JTM45/100, JTM50(x2), 2203
- zrAC/DC
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Re: Problem with voltages on V3
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.
~~Current Amps~~
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
- zrAC/DC
- Senior Member
- Posts: 267
- Joined: Sat Nov 24, 2007 11:03 pm
- Just the numbers in order: 7
- Location: Waterloo, NY
Re: Problem with voltages on V3
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.
~~Current Amps~~
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
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Re: Problem with voltages on V3
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.zrAC/DC wrote: I thought I might of had a bad 470k resistor but 100% positive.
- zrAC/DC
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Re: Problem with voltages on V3
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!
Sounds really good, I can't see how it can get better
Thanks Steve!
~~Current Amps~~
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
1.) JTM45
--------Terawatt--------
http://www.reverbnation.com/terawatt" onclick="window.open(this.href);return false;
http://www.myspace.com/terawatts" onclick="window.open(this.href);return false;
- Beavis
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Re: Problem with voltages on V3
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.
Kind of wish I would of searched the forum a lot sooner for the problem. This thread was like the 3rd on the list.
"Humanoid's in trouble and it's scared out of its wits."