Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: goldstache on November 02, 2012, 11:23:51 am

Title: Blues Deluxe Reissue channel switching and reverb help
Post by: goldstache on November 02, 2012, 11:23:51 am

Hello all, I am looking for some help diagnosing a channel select/reverb problem.  I checked all my Test Points (30-36) and can't seem to understand where my problem lies. 
Here are some of the voltages:
TP30
-14v steady
+16v channel change

TP31
nominal voltages

TP32
+16v drive channel selected (supposed to be -16v!!!!)
+16v normal channel (supposed to be +7.5v)

TP33
nominal voltages

TP34
+.082v reverb off
-17.43v reverb on (supposed to be -1.38v)

TP35
+.7v off
-33.1 v on (supposed to be -2.2v!!!!!  Blown Diode????)

TP36
16.35 v off
16.33v on  (supposed to be -15.6v!!!!!)

Also K1 is ticking when I select drive channel and the reverb is on with footswitch plugged in.

With footswitch unplugged.  Only drive channel has reverb.  No reverb on the clean channel at all!

Checked +16v/-16v supply and it checks good. 

Checked the 5watt resistors and they appear to be good. 

Reflowed all joints on board.

Help!!!!!!!!!!!!!!
thanks

Title: Re: Blues Deluxe Reissue channel switching and reverb help
Post by: PRR on November 05, 2012, 12:19:06 am

You are going to have to point to a schematic. The ones I found don't have a TP35 TP36.

Title: Re: Blues Deluxe Reissue channel switching and reverb help
Post by: goldstache on November 07, 2012, 09:37:02 pm

Here is an update.  After replace U3, K1, and K2.  I have reverb and channel switching flawless without footswitch.  But with the foot switch, reverb switches good.  But, the drive channel is silent.  And it takes a few seconds for the led on the amp control panel that indicates channel to illuminate or turn off.  It must be a cap having trouble powering up.  So......  I guess I need to try to narrow it down to just the footswitch and associated path to the relay sections of the amp.
Any thoughts?
Thank you.

Title: Re: Blues Deluxe Reissue channel switching and reverb help
Post by: OldHouseScott on November 08, 2012, 08:59:22 am

This looks like it might be the correct schematic.

http://support.fender.com/schematics/guitar_amplifiers/BluesDeluxe_Reissue_2004_schematic_Rev-A.pdf (http://support.fender.com/schematics/guitar_amplifiers/BluesDeluxe_Reissue_2004_schematic_Rev-A.pdf)

Title: Re: Blues Deluxe Reissue channel switching and reverb help
Post by: PRR on November 09, 2012, 12:48:34 am

Looks like a diode-orgasm in the switching.

Looking at the plan Scott points at:

Check TP33 against the notes lower-left 1st page. Is it going a full + and - 15V, or falling short?

Also TP31 TP32.

Is your "+16V" really 16V?

5W resistors R78 R79 are correctly rated, but I hear on some models they are packed too tight and the solder joints go bad (or the board toasts). Examine.