Peavey Encore 65 problems

[dukeofurl]

Hello... been a long-time reader of this forum and really enjoy alot of the troubleshooting topics!

Right.. I have a Peavey Encore 65 that has had it's case cut down to a head-size unit.
No reverb pan installed. - Leads to my first question: Is there any problem with running this amp without a pan connected?

I have re-capped the amp but now have problems with the 6amp fuse (F4) blowing after awhile of playing. (around half an hour-ish).

Any idea of where to begin to track down this problem?

I really appreciate any input you may have.

[Jazz P Bass]

I would not think running the amp without a pan would be a problem.
Keep the reverb control at "0".
As to blowing the 6 amp heater fuse.
What caps did you replace?
A power tube shorting plate to heater will blow the fuse.

[dukeofurl]

Thank you for your reply!!
I replaced:
C1, C17, C36, C39, C40, C41 C43, C44, C45, C46, C47 with same values and some with slightly higher voltage values (due to not being able to buy the same as original)

[olddawg]

How old ore the output tubes? That's the first thing I would do. Swap in a new set. As a starving musician I had this happen several times. I don't recommend it to anyone, but I wrapped the output tubes in a bar towel and tossed them on the carpeted floor a couple of times. It broke loose the shorts and got me through the night without blowing a fuse every 5 minutes.

[dukeofurl]

Funny enough; I thought the 6l6's "may" be at fault and did replace them with no change except for one of the tubes glowing brighter than the other in the new set. - That's when I decided to post here.

By the way, interesting trick with the towel.

[dukeofurl]

Update:
Today I checked all of the tubes with my trusty tubetester... All measure good except the 12AT7 which is questionable but no shorts.
*Am I correct in assuming that the 12at7 is for the reverb circuit only?

[dukeofurl]

Can anybody shed some light on how the HUM BALANCE control should be set?

[Jazz P Bass]

Update:
Today I checked all of the tubes with my trusty tubetester... All measure good except the 12AT7 which is questionable but no shorts.
*Am I correct in assuming that the 12at7 is for the reverb circuit only?

No it is not.
The reverb signal goes into V3 (12AT7) pin #7.
The recovery from the reverb tank is applied to V2 (12AX7) pin #7.
The other half of V3 is used to drive the Preamp Out jack.

As to the Hum Balance Pot.
The pot is used to "balance " the current draw of the heater circuit.
With no signal applied, monitor the speaker connectors for Vac.
Turn the pot until you have the lowest Vac reading that you can obtain.

[dukeofurl]

As to the Hum Balance Pot.
The pot is used to "balance " the current draw of the heater circuit.
With no signal applied, monitor the speaker connectors for Vac.
Turn the pot until you have the lowest Vac reading that you can obtain.

Ah-ha!... this is interesting! - Wondering if this is not set up properly. Will put everything back together and check.

[dukeofurl]

Okay... finally got the board re-installed and want to power up for the first time using a lightbulb limiter.
I've just built a lightbulb limiter and need to know....
Do I power the amp up with all tubes removed or only the 6l6's? - and I leave the amp in STANDBY... Correct?

[52 Bill]

Either way. I'd start without the power tubes just to see if the amp runs ok without them. Then add them to see what happens.

Plug the amp into the limiter, then turn on the amp. Watch the light bulb to see how bright it gets. Normally there will be a slight turn on flash when the amp first turns on, but then the bulb should dim. Once the amp has been on for a bit turn the standby switch off and see what happens.

If the amp is drawing too much current the bulb will light up almost to full on. If this happens, you need to go back and find out what is causing the amp to draw so much current.

If the light stays fairly dim, try the entire procedure again with the power tubes installed.

[dukeofurl]

Thank you for your reply 52 Bill, - Do I leave the preamp tubes in or leave them out as well?

[52 Bill]

They draw such little current, I'd put them in and leave them until they prove to be a problem.

[dukeofurl]

Before going any farther, I decided to try to check as many components as possible. One of my discoveries was that the diodes on the bridge were found to be IN5408 (x4) in place of IN4007 (CR6, CR7, CR8 & CR9). It appears obvious that somebody has been inside this amp at some point. (they had to hardwire a track that had been burnt in that area (around C42 area) but looks like a good repair.

I have some IN4007 diodes.... I would like to get this thing back to stock.. Is there any reason why not to replace these diodes?
I've been through to replace all of the 1W 220k resistors so far. (the originals were "okay" but drifting.

[Jazz P Bass]

I would not mess with the diodes.
Both are rated at the same voltage.
The 1N5408 can handle a lot more current.
Kind of like a big brother.