Peavey triumph 120 blows fuse F5A on power up....??

[wheatley]

I got a this triumph 120 combo two years ago and had to retube it and replace the 8 amp fuse. The amps been working well since until the other night. During an hour or two of normal playing the amp cut off in the middle of a song with no strange noise, like it was unplugged. I opened it up and the ceramic fuse F5A was blown. I replaced the original ceramic ABC5 with a glass AGC5, both 5 amp 250V fuses. Currently the amp is blowing this AGC5 fuse immediately on power up, with and without the power tubes in. In the schematic im using this fuse is labeled F2 and is between the power cord and the transformer Any suggestion on where to go from here would be great.

[tedmich]

I'd start by testing the (4) screen grid resistors, which if one is bad should all be changed to 1k at 5w. Do you have the schematic PDF from Peavey?

[Enzo]

OK, there is an 8A fuse for the heaters. The mains fuse is a 5A.


Just to be sure, you have the Triumph, with 10 controls across the front and a push switch in the center? Or a Triumph PAG, with 13 controls across the front and two push switches? I always get scared when I read "the schematic I am using..."


Don't tell me two years ago, tell me now, are you only blowing the main fuse?


Isolate the problem. I see four internal fuses, note where they go and remove them. Verify they are all the proper value. Now does it still blow the main fuse when turned on? If it still blows the main fuse we have trouble, but if it holds the main fuse while the other fuses are out, then we re-install each of those fuses one at a time to see which one/ones are involved.

Now I have been saying blows fuses, but what you need to do is look up "light bulb limiter", then make one and use it. Very simple tool , but very helpful, and it takes the place of blowing lots of fuses.

[wheatley]

i got the shematic from this website......

http://elektrotanya.com/peavey_trium.../download.html

[wheatley]

its the one with ten pots and the center button. with the light bulb limiter the light staying bright would be a sign of a problem correct? any ways I'll try pulling the other fuses real quick

[wheatley]

so i made a light bulb limiter, took out all the power and pre amp tubes, then tried what you said. it seems that fuse F1, 1 amp slow blo, is the one causing the light to stay bright. with F2 and F3 pluged in light bulb limiter stays dim and the amps fan comes on along with the red power light.

[wheatley]

Alright so diode cr12 is reading 0v in both directions so i pressume that is bad. would that have taken out out anything else that i should test? the 100 ohm screen grid resistors all read good. thanks for all the help yall. im tryin to get this thing back for some recordings next week

[Enzo]

OK, so the high voltage supply seems involved. probably not, but does it matter if the standby switch is on or off?

Next to the fuse are four diodes. Any of them shorted? Aha, you already checked those.


Go to your empty power tube sockets, is there a low resistance from pin 3 to ground on any socket? Or on the power tube board, there are two diodes in the center of that board, is either shorted?

[wheatley]

i took it off standby and nothing changed, the green light didnt come on. from ground to pin 3 the ohms moving up and down between about 6 Mohms and 60 Mohms. all the other diodes check out so i guess im gona swap that cr12 diode out and see what happens.