New Guy, 5150 question.

[Twist]

Which model are you working on? EVH 5150 or 5150 II ? You mentioned Reverb ?

[Amp Kat]

If the tubes are cold and not lighting you most likely found your problem and you have to find why they aren't lighting. The 5150 uses elevated heaters on a few of the preamp tubes and they run them in series 12 volt operation if I'm not mistaken. You may have a cold solder joint on a socket or maybe a bent pin or bad connection or socket on the board. Check your voltage from ground to pins 4 & 5 on the preamp tube sockets.

[Enzo]

REverb? If there is reverb, then it must be a 5150 Combo, not a 5150.

[Danglin' Fury]

My pretubes V5 and V3 aren't lighting up. The plate resistors are good but the voltages seem a little high. I noticed a guy that asked how to ohm the OT but the reply mentioned a blue and a brown wire. I have red, yellow and orange. How would I go about ohming this little fella as I have a 2x12 combo. I am getting pretty high voltages in my circuit right in the voltage divider after the rectifier. I know it's not the tubes as I have changed them w/ known good tubes. Thanks for looking and any response welcome.

[Twist]

Could you post a schematic of the model you have on here. I don't have a schematic of a 5150 with reverb.

[Enzo]

The model is "5150 Combo" and it is posted in the Enzo gallery at www.ampix.org

[Danglin' Fury]

EUREKA!!!!!!! I fixed this bastard 5150!!! I wasn't getting my -23 volts anywhere, so I checked R116 and R117 as that's where the + and - 25 turns into + and - 23 and both of those were open. Now this thing is a tone behemoth. I still have a problem with the amp popping when I change channels and the reverb on this combo acts like a gain boost/mid cut when I turn the pot. I have changed both of the J-FETs that are the clamps for stopping the pop but that didn't stop the problem. Any other suggestions as I'm not too familiar w/ reverb circuitry.

[Amp Kat]

Nice job on the fix. If you look at that schemo you'll see the +/- 23 & 24 are also used as a 50 volt elevation for the preamp tube or at least V2. Something in that circuit shorted causing R-116 & R117 to blow as they are both almost fuses basically. Did you check R55,63,110 &111 also ? Could be a leaking cap in that 50 volt circuit gone from that short.

[Danglin' Fury]

Thanks, Amp Kat! I didn't check those resistors specifically. The guy needed his amp for a gig and I gave it back to him as is. He was very grateful. I told him I would be over at his house next weekend to fix the popping. I let it run for 3 hours and took it off standby periodically and jammed. It sounded every bit as good as a 5150. I am concerned about the popping and the reverb not working. I'm also wondering about Q12 and R74, R70 and C40. Probably that whole circuit from Q8 on left. Peavey said that was where the clamp circuit is generated. Just found that out. Gonna check it this coming weekend @ his house.