"The Twin" is HOT!!!

drewl · 11-11-2008, 02:52 AM

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 · 11-11-2008, 03:54 AM

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 · 11-11-2008, 07:34 AM

Also, what is your filament voltage?

Chuck

Enzo · 11-11-2008, 10:35 AM

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

And don;t call me SHirley...

(Sorry, couldn;t resist)

drewl · 11-11-2008, 12:37 PM

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 · 11-11-2008, 10:51 PM

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 · 11-12-2008, 12:47 AM

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 · 11-12-2008, 05:07 PM

Quote:

Originally Posted by drewl

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 · 11-12-2008, 07:27 PM

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 · 11-13-2008, 08:26 AM

Quote:

Originally Posted by Enzo

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

And don;t call me SHirley...

Thanks Enzo

11-11-2008, 02:52 AM	#1
drewl Senior Member Join Date: Jun 2006 Posts: 556	"The Twin" is HOT!!! 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.

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11-11-2008, 03:54 AM	#2
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	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?

11-11-2008, 07:34 AM	#3
Chuck H Old Timer Join Date: May 2007 Location: pacific north west Posts: 1,483	Also, what is your filament voltage? Chuck

11-11-2008, 10:35 AM	#4
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	It is the power source for the heaters..... And don;t call me SHirley... (Sorry, couldn;t resist)

11-11-2008, 12:37 PM	#5
drewl Senior Member Join Date: Jun 2006 Posts: 556	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.

11-11-2008, 10:51 PM	#6
52 Bill Old Timer Join Date: Jun 2007 Posts: 1,253	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.

11-12-2008, 12:47 AM	#7
drewl Senior Member Join Date: Jun 2006 Posts: 556	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?

11-12-2008, 07:27 PM	#9
drewl Senior Member Join Date: Jun 2006 Posts: 556	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.

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