Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on February 11, 2014, 11:08:43 am

Title: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 11, 2014, 11:08:43 am: I may as well take advantage of you all while I'm here.
A Fender deluxe reverb came in this morning. Point to point wiring. Fitted with two 6L6 's that I swapped for 6V6 as fitted originally. I've redone the bias. Very cool sounding amplifier.
( my favorite of all Fender's ). The issue is the reverb. Reverb tank being unplugged, no cord in any input as well, a loud squeal is heard when the reverb volume is turned past 4 -5.
What could it be ?

thanks

Colas
Title: Re: DELUXE REVERB w/boost control
Post by: sluckey on February 11, 2014, 11:16:41 am: Plug in the tank. Does the squeal go away?
Title: Re: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 11, 2014, 11:27:41 am: when the reverb tank is plugged, same issue, no difference at all

Colas
Title: Re: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 11, 2014, 11:54:45 am: the reverb volume acts as a presence, the more its been turned clockwise, the more trebly the tone becomes until the squeal appears
removing v4 solves the problem but the volume is considerably lowered , swapping v4 for a new tube doesn't cure the ill....
this thing upsets me and..my ears....
Title: Re: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 13, 2014, 07:04:26 pm: trouble solved:

1 bad cap and one lead unsoldered...........6 hours............

Colas.
Title: Re: DELUXE REVERB w/boost control
Post by: HommeMarrBuckley on February 14, 2014, 10:05:27 am: Could you post a gutshot pic of the point to point wiring? Just like to see.

Glad you got it resolved.
Title: Re: DELUXE REVERB w/boost control
Post by: Willabe on February 14, 2014, 10:14:24 am: Quote from: Colas LeGrippa on February 13, 2014, 07:04:26 pm
1 bad cap and one lead unsoldered

Which cap? Was it in the reverb circuit?

Brad :dontknow:
Title: Re: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 15, 2014, 10:54:09 am: Hi,

a white lead from the reverb 100k pot going to a 470k resistor was disconnected. I soldered it to its place but that didn't cure the issue. The problem went away when I replaced ( at the same time ) 5 cathode bypass caps. But I still can't figure out which one caused the high pitch squeal. I replaced as well the 1/4w ( or is it 1/8 w ? ) phase inverter LTP resistors to BF values ( 470 and 1 M, 1/2w , see pic b4 the replacement ). The reverb input tube was microphonic ( although not causing audible noise except when tapping on it , and not causing the squeal), and the the output tubes were 6L6's, that I swapped for 6V6's and re biased using a 1 OHM 1 % resistor. The amp is a new one now !

Colas
Title: Re: DELUXE REVERB w/boost control
Post by: Willabe on February 15, 2014, 03:58:14 pm: I'm betting it was the verb return K bypass cap.

Quote from: Colas LeGrippa on February 15, 2014, 10:54:09 am
The amp is a new one now!

Good job Alvin!

Brad :icon_biggrin:
Title: Re: DELUXE REVERB w/boost control
Post by: HotBluePlates on February 15, 2014, 04:22:37 pm: Quote from: Colas LeGrippa on February 15, 2014, 10:54:09 am
a white lead from the reverb 100k pot going to a 470k resistor was disconnected. ...

Someone wanted to kill the pull-boost function of this amp.
Title: Re: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 16, 2014, 05:40:52 pm: Quote
Good job Alvin!

Thank you brother Will, I always do good jobs. Very seldom in amps, though hey hey !
Title: Re: DELUXE REVERB w/boost control
Post by: Willabe on February 16, 2014, 06:45:52 pm: You glad to be home and off the road?

Where'd you go?

Brad :m2
Title: Re: DELUXE REVERB w/boost control
Post by: Colas LeGrippa on February 17, 2014, 11:16:43 am: here, there and everywhere, with my blues band and the woodstock tribute, no international tour though just in Canada

Alvin
Title: Re: DELUXE REVERB w/boost control
Post by: Willabe on February 17, 2014, 11:58:11 am: Quote from: Colas LeGrippa on February 17, 2014, 11:16:43 am
here, there and everywhere, with my blues band and the woodstock tribute, no international tour though just in Canada

Here, there and everywhere, Canada's a mighty big piece of land Alvin!

Brad :laugh: