Peavey 5150 head on bench, 4x 6L6 model. Blown internal HT fuse. Fuse was 1A, but schematic shows 2A fast, so that might be part of the problem. User was also pushing a 4ohm load with the 8ohm tap.
Anyway, trying to identify this component. Looks and talks like a resistor (R210 on schematic) but I don't know the value. Says, "400W 10FP" on schematic. I can make out "DALE, 10W, 10%" on the component, but other text is too light to make out.
It measures open (actually, reads 26M...I unplugged the board's connectors and I THINK this component is isolated from e-caps).
5150 on bench
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5150 on bench
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I build and repair tube amps. http://amps.monkeymatic.com
Re: 5150 on bench
OK, I think I get it. "400W10FP" is 400 ohms, wirewound, 10 watts, flame proof. Toasted, but not incinerated.
I build and repair tube amps. http://amps.monkeymatic.com
Re: 5150 on bench
That's the power resistor that the 5150's use instead of a choke----- that one looks heat damaged.
Just wait until it's time to change screen grid resistors on that amp---- you have to drill out the rivets holding the power tube sockets in place (to remove the power PCB)----- replace the bad screen grid resistors (mounted on the bottom of the power PCB) and then rivet the power PCB back into the chassis.
I had to buy a rivet gun to do the first one that came to me----- it has well paid for itself since then----- there are a lot of used 5150/6505 amps out there....................... gldtp99
Just wait until it's time to change screen grid resistors on that amp---- you have to drill out the rivets holding the power tube sockets in place (to remove the power PCB)----- replace the bad screen grid resistors (mounted on the bottom of the power PCB) and then rivet the power PCB back into the chassis.
I had to buy a rivet gun to do the first one that came to me----- it has well paid for itself since then----- there are a lot of used 5150/6505 amps out there....................... gldtp99
Re: 5150 on bench
Wow. On reassembly, why rivet instead of bolt?gldtp99 wrote:rivet the power PCB back into the chassis
Finally, my old Knight tube tester came in handy. Identified shorts in two of the four power tubes.
Got a new fuse and wirewound resister installed, and a new set of tubes. Working good. Biased (non adjustable!) at about 55% dissipation. As they say elsewhere on the net, this bitch is cold. Plates at 485, screens at 481.
I build and repair tube amps. http://amps.monkeymatic.com
Re: 5150 on bench
yes, you got it.xtian wrote:OK, I think I get it. "400W10FP" is 400 ohms, wirewound, 10 watts, flame proof. Toasted, but not incinerated.
In fact you can propose to the customer an upgrade of the amp while you are on it. A choke instead of that resistor, and a smaller coupling cap after the second stage would improve the overall clarity, expecially on low tuning and hi volumes. Of course a mod for the bias (usually as cold as on mesa rectifiers) would improve the situation.
Re: 5150 on bench
About five years ago, I replaced the output tube board in my friends 5150 w/ an aluminium plate and chassis mounted sockets in PTP fashion. Wasn't too difficult. Also added adjustable bias. The power R in question is indeed 400R/10W, but I do like the choke idea. Nothin wrong w/ making an amp mo better, this one's been a solid work horse- 2 US tours, countless rehearsals/studio time etc..
Was wondering if any amp builders on this board have used something like these instead of the bulky WW resistors??? Are they equal, better, worse? http://www.mouser.com/ds/2/303/tbh-180081.pdf
Was wondering if any amp builders on this board have used something like these instead of the bulky WW resistors??? Are they equal, better, worse? http://www.mouser.com/ds/2/303/tbh-180081.pdf
Re: 5150 on bench
If you have to change the screen resistors. you can unsolder them and let them drop out, then replace them on top of the board. Saves a lot of time with the rivets. Have you checked them yet?
Re: 5150 on bench
The next amp I design will use something similar, but I am keeping my cards close to my chest until I am done.Masco wrote:About five years ago, I replaced the output tube board in my friends 5150 w/ an aluminium plate and chassis mounted sockets in PTP fashion. Wasn't too difficult. Also added adjustable bias. The power R in question is indeed 400R/10W, but I do like the choke idea. Nothin wrong w/ making an amp mo better, this one's been a solid work horse- 2 US tours, countless rehearsals/studio time etc..
Was wondering if any amp builders on this board have used something like these instead of the bulky WW resistors??? Are they equal, better, worse? http://www.mouser.com/ds/2/303/tbh-180081.pdf
Ryan Brown
Brown Amplification LLC
Brown Amplification LLC
Re: 5150 on bench
so the screen resistors were good?
Re: 5150 on bench
Hi. They measured fine, and the amp sounds good.jamme61 wrote:so the screen resistors were good?
I build and repair tube amps. http://amps.monkeymatic.com
Re: 5150 on bench
All this time I've been doing it the hard way! Actually it does not take that long to drill them out. Hardest part is getting the old rivet past the mounting ears on the tube sockets. However, I will try this other method next time a I get a 5150 or Ultra in for repair.
jamme61 wrote:If you have to change the screen resistors. you can unsolder them and let them drop out, then replace them on top of the board. Saves a lot of time with the rivets. Have you checked them yet?