New 5150 owner, need some help

[the_unknown]

I will try to keep this as short as possible. I found a signature 5150 today on craigslist with a blown tube (the owner didn't know which one, nor do I)
I picked it up for $350 on the assumption that it just needed tubes. I got it and went to my local shop and bought all new GT 6L6's and Mesa 12AX7's for it.

I went to a friends house who knows tube amps pretty well (has a sig 5150 and block letter 5150) He helped me replace the tubes since this is my first tube amp. Changed out all the tubes, and then plugged it in. Everything seems to work (standby light worrks properly and all lights appear to work)

Unfortunately no sound is produced. The pre-amps light up (i think, i didn't see them illuminated but they were warm to the touch) but the power tubes did not light up at all. Anyone have any idea why this is? (hint hint Enzo )

CN: preamp tubes appear to work but no power tubes work

[the_unknown]

Well after doing some more research, I think I may have narrowed down the problem. It sounds like it may be a fuse or I have a jumper that is loose on the power tube connection. I've looked for some detailed instructions on removing the board but I have come up short. What all needs to be done to remove the board from the head?

[CharlieP]

I will try to keep this as short as possible. I found a signature 5150 today on craigslist with a blown tube (the owner didn't know which one, nor do I)
I picked it up for $350 on the assumption that it just needed tubes. I got it and went to my local shop and bought all new GT 6L6's and Mesa 12AX7's for it.

I went to a friends house who knows tube amps pretty well (has a sig 5150 and block letter 5150) He helped me replace the tubes since this is my first tube amp. Changed out all the tubes, and then plugged it in. Everything seems to work (standby light worrks properly and all lights appear to work)

Unfortunately no sound is produced. The pre-amps light up (i think, i didn't see them illuminated but they were warm to the touch) but the power tubes did not light up at all. Anyone have any idea why this is? (hint hint Enzo )

CN: preamp tubes appear to work but no power tubes work

One of your internal fuses may be blown. It is not uncommon at all for one to blow when you have a bad power tube. You did the right thing by getting new tubes. Now you have to investigate a little farther. Use a multimeter to check fuses, do not just do a visual check. Sometimes fuse is bad where you can't see the filament. Use the correct replacement value fuses. Some are fast blo and some timed. Fuses are probably 5mm x 20mm long. Hope this gets it back working for you.
Sounds like a Steal!

[Enzo]

You may have an open heater fuse inside or as you surmised, the ribbon cable over to the power tube board may have a failed pin.

No heaters - no sound.

[the_unknown]

Thanks for the responses guys, I got it apart and all the fuses were ok. I then noticed I had a bad connection near the fuses where the yellow wire plugs into the board. I went to radioshack and found a similar connector, soldered in a new male and female pin. Voila! it lights all the tubes now and it sounds great! The rhythm pot is a little scratchy but thats no big deal for now. Thanks again guys, i appreciate it

OT: Enzo, I have a buddy (the one with the 2 5150's) who wants to become a certified peavey tech for this particular amp. Any suggestions on how he could go about doing this?

[Don Moose]

If you decide to go about cleaning that scratchy pot, use POT cleaner, not contact cleaner.

Also - it may be scratchy because a coupling cap before or after it is leaking DC. Only worry about that if the pot cleaner doesn't help, though.

Hope this helps!

[CharlieP]

If you decide to go about cleaning that scratchy pot, use POT cleaner, not contact cleaner.

Also - it may be scratchy because a coupling cap before or after it is leaking DC. Only worry about that if the pot cleaner doesn't help, though.

Hope this helps!

What is different about the pot cleaner?

[Enzo]

Contact cleaners are solvents - period. Pot cleaners like Deoxit are a lubricating cleaner.

[Ptron]

At the risk of hijacking: I've been using whatever contact cleaner I have to "flush out" the pot and then spraying some Caig MCL (moving contact lubericant). I should not be doing this?

[Enzo]

Whatever works.

Pots come with a lubricant in them, solvent cleaners remove this lubricant. The MCL does indeed leave a lubricant behind, but it is a matter of removing what is essentially a light grease and replacing it with a light oil.

The MCL is meant as a contact surface lubricant to reduce wear of the contacts. The lubrication of the mechanical aspects - shaft bushing for example - are secondary to its purpose.

I believe in using the least chemical assault that yields good results. If a simple squirt of MCL alone does the trick, why go through the added steps? For me the MCL by itself cleans pots 99% of the time.

[bluesfreak]

When having the 5150 working again I would recommend checking bias. Unfortunately the 5150 has a fixed bias (no pot but a fixed resistor in the circuit) and usually runs ice cold (talking about 11-17mA at 480V). Adjusting the bias into a more normal range (usually 75-80% of max. Power, requires small change to circuitry) makes the 5150 sound even better and can switch it into a firebreathing beast *g*...

just my 2c
bluesfreak

[WOLGAR]

5150

I have had lots of 5150 and 6505 heads. Pull the four screws out of the bottom of the amp. Then slide the amp out the back of the case. Flip it over after you get it out of the case. There are 4 or 5 fuses on the board. If those are not blown check the big flat gray jumper wires. Take them off and check .also before taking your amp apart. Check the fuses on the outside of the amp on back. Then get some contact cleaner and spray the effects loop jacks. They can cut the sound out by being dirty. Take a guitar cable and plug one end in the send and the other in the return on the effects loop. If the sound comes on.its a bad effects loop. Or ,turn your guitar down and plug it into the return in the effects loop. Then turn your volume up on the guitar. If you have sound, its in the preamp section or the effects loop. Wolgar

[Enzo]

OT: Enzo, I have a buddy (the one with the 2 5150's) who wants to become a certified peavey tech for this particular amp. Any suggestions on how he could go about doing this?

Sorry, I meant to respond earlier.

Peavey - or anyone else I am aware of - doesn;t certify people for work on a specific model. What an "authorized service center" means is an agreement between Peavey and a repair shop. It means they feel your are competent to service their products in a reliable and convenient manner for their customers. it is not a certificate of accomplishment, like a merit badge.

In the service business, there is no real difference between amps. Oh of course they sound different, and use different tubes and all, but there is nothing unique about working on a 5150 compared to an Ultra or a Classic 20 from an electronic point of view. SO a tech is competent to work on all of them or he is not. There are no certificates for individual models.

Fender has their Bronze, Silver, and Gold tech certificates, but again, they are not specific to models. They are intended as a measure of overall competence to service their products - sort of a varsity and junior varsity thing.