Oh Shiiiii.... My amp is not working!

[RockNRoling]

I just got this head last week and it has been working perfectly so far... It is a Lee Jackson designed AMPEG VL 1002 100Watt head. I tried to power it on tonight and the power lights came on, but not the lights that light up the logo. Wait a minute and click on the standby and I got no sound. I look behind the amp all the 12ax7s are lit but the one right next to the power amp tubes. The power amp tubes are not lighting up either.... Both Fuses seem okay and even if one of the power amp tubes went out the other pair would still light up right?? Nothing smells burnt... Can somebody help me out???

 

[RockNRoling]

Re: Oh Shiiiii.... My amp is not working!

I was just reading some of the Harmony Central reviews of this amp when I ran across this... This sounds exactly like what I am dealing with.

Reliability : 1
This is where the amp has tottally failed me many times,
within a year after purchasing it used on ebay for 600 american dollars , I played a gig and there was no sound from it
I checked fuses they were ok
The front lights were out and the power tube heaters.
after taking it to the shop I learned that Lee JAcksons design of connecting the lights to the power tube heater power was flawed , he used cheap molex connecters and the power passed through the preamp board then got jumpered to the power amp board then finnally to the front lights,
Instead of wiring the lights and the poiwer tube heaters directly to the transformer, so what Was found in the amp was melted ,no kidding, melted plastic molex connecters and burnt spots on the circuit board.
The connecters were replaced, and the power was rerouted directly from the transformer.
Lousy idea in my opionion TO JUMPER 6.3VAC HEATER POWER THROUGH 2 OR 3 CONNECTERS FORM BOARD TO BOARD TO GET TO THE POWER AMP HEATERS?the most important section of the amp.
Was he high when he designed this section of the amp?

Can I fix this, or do i need to get it taken in??

 

[Rich_S]

Re: Oh Shiiiii.... My amp is not working!

If that's what happened to yours, I would recommend getting rid of the connectors and hard-wiring the whole heater string like a normal old-style hand-wired amp. The heaters (filaments) draw a decent amount of current, and don't take kindly to loose connections. They heat up, and eventually burn up.

Open that baby up and post some pics of the guts, but don't touch anything, unless you know what you're doing and know where the high voltage is.

 

[RockNRoling]

Re: Oh Shiiiii.... My amp is not working!

I think that is exactly what happened... here is what I found

 

[RockNRoling]

Re: Oh Shiiiii.... My amp is not working!

that is right by where the power tubes connect to the board (the bottom pics you can see the circle where the first 6550 lies...

 

[Rich_S]

Re: Oh Shiiiii.... My amp is not working!

Holy &^%*!!! 6550's in board mounted sockets?!? Shame, shame on you, Lee Jackson.

I assume that burned-up blue wire is coming from the power transformer, and is supplying filament current to the output tubes. 6550 heaters draw 1.6 amps each; 6.4 amps is a substantial amount of current, and it looks like those little knife-edge stab connectors can't take it. The way it works is, the bad connection has trouble passing current, and gets warm. This causes oxidation, making the connection worse, making it get hot. Eventually, the whole thing burns up, at which point the current stops flowing, and it all cools off, only the amp's not working.

It's hard to tell exactly what's what in those pics - can you identify which of the pins is "1" on the tube socket, or mark which way the nub in the tube base is pointing? The 6550 has its heater connected on pins 2 and 7, but we need to know where "1" is first.

I'd say get it to a tech, and tell him you want the heater traces on the PC board cut, and replaced with a traditional twisted pair, daisy chained across the board from socket to socket. Replacing the Molex connector is futile, it will just happen again in the future.

Are those black wires with the pink Sta-Con connectors going to the front panel lights? With some creative soldering and/or use of crimp-on splice connectors, you might be able to back-feed the heater bus through the black wires' connectors - they seem to be able to handle the current better.

Another (certainly easier, perhaps overall better) idea would be to keep using the existing traces on the board to distribute heater current, but solder the burned-up wire directly to the main trace. It actually looks like somebody already did that with the other wire in that pair. It's hard to tell in the photo - does it look like there might have been an additional pole on the end of that connector, which has been removed? That little lump of solder holding the blue wire on the trace at the edge of the board doesn't look original - it wouldn't make sense to use the connector for 8 wires, then solder the ninth wire on. I'll better the connector was originally 9-pole.