"The Twin" is HOT!!!

[drewl]

Got some doozy's this week.
Replaced the fried/loose power resistors in a "The Twin" and let it cook for a few hours, dang this thing is hot, tranny's are hot, chassis is hot, handle is hot.....is it supposed to be this hot?
Don't think I've run one more than an hour or so......but this thing is hot.

[Enzo]

So what sort of idle current are the tubes running on? Have you scoped the output for RF? Have you checked mains draw? How many watts is it burning just idling?

[Chuck H]

Also, what is your filament voltage?

Chuck

[Enzo]

It is the power source for the heaters.....


And don;t call me SHirley...


(Sorry, couldn;t resist)

[drewl]

The bias current (if that's "idle" current) is just fine, I always scope outputs when repairing, and it's clean no RF or osc. of any kind.
I'll check heater voltage.
The 25K and 2.5K voltage dropping resistors in the supply were loose & burnt the board, I'm guessing the replacements are throwing off some heat also.
They're 10w resistors, so they're gonna get warm.

[52 Bill]

Weird, I've got two in the shop right now.

One has an open primary winding on the power transformer, probably overheated. The other one has too many issues to list here, but it does get warm after running awhile.

[drewl]

I've also got one with an open primary, hmmmm.....
oh, and Enzo if you read this Fender does have the original trannies.

So, we know those cement block resitors fail, there may be too much stress on the power trans since we've got a couple with open primaries.
Wonder if there's a better way to set up the power supply.
I was reading a thread on changes made to the HD Deluxe from Fender, did they ever come up with an engineering change for these?

[52 Bill]

I've also got one with an open primary, hmmmm.....
oh, and Enzo if you read this Fender does have the original trannies.

According to their website, Fender still has a few of the export version of the transformer available.

[drewl]

My friend (who's shop I do repairs for) is a Fender dealer, so he was able to order the tranny from the original part number.
We'll see if it's the export version or not.

[Chuck H]

It is the power source for the heaters.....


And don;t call me SHirley...

Thanks Enzo