Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on May 18, 2011, 04:47:06 pm

Title: Fender Super 60 Volume Problem
Post by: plexi50 on May 18, 2011, 04:47:06 pm: The Clean channels volume is very low. At full CW position it is audible but is very low. The Overdrive channel is fine. I have been looking at the OP1 & OP2 voltage regulators (I think thats what they are) I wanted to call them LDR's but i am not sure. I have checked all resistors in the signal path for the clean channel and they are reading there spec values. Also checked cathode resistor and cap. Also plate resistor for V1B clean channel. Channel switching works with footswitch and front panel switch. :help: I think it's time to make a signal source to inject into the input and track it down where the signal drops out

Schematic. http://www.triodeamplification.com/files/super_60_rack.pdf
Title: Re: Fender Super 60 Volume Problem
Post by: plexi50 on May 18, 2011, 06:57:21 pm: I have done some reading and what i have found is the OP is made by Vactec. One link i found says it is a Fenders part number.

I removed one to get the part number. 21L915. Any info on this part or sub?

Could i remove Z1 and all the OP's and bypass them. I would loose the channel switching and maybe reverb. Have to look some more at the schematic later

I found these at Newark. I cant find any info on the Vactec 21L915 part number.

http://www.newark.com/excelitas-tech/vtl5c4-2/optocoupler-resistor-2500vrms/dp/98F3997
Title: Re: Fender Super 60 Volume Problem
Post by: plexi50 on May 20, 2011, 04:07:03 pm: I quess i will order these parts from Newark and see what happens
http://www.newark.com/excelitas-tech/vtl5c3-2/optocoupler-resistor-2500vrms/dp/97F1139

They are 5 pole center CT ground even though the info on the Newark site says 4 pole. There error
Title: Re: Fender Super 60 Volume Problem
Post by: plexi50 on May 25, 2011, 08:25:23 pm: Got the LDR's from Newark and installed them today. Changed out the (2) .0047 coupling caps out to .022 values. Clean channel is louder than before and amp sounds good
Title: Re: Fender Super 60 Volume Problem
Post by: Willabe on May 25, 2011, 10:12:37 pm: plexi 50,

Nice job! No way would I have had the patience to work that out.

Brad :icon_biggrin:
Title: Re: Fender Super 60 Volume Problem
Post by: plexi50 on May 26, 2011, 07:48:07 am: Quote from: Willabe on May 25, 2011, 10:12:37 pm
plexi 50,

Nice job! No way would I have had the patience to work that out.

Brad :icon_biggrin:

Me niether. Actually i have been dabbling in more SS intergrated amps latley. Not my cup of tea. I figure if i dont learn more about the functions of SS parts and LDR's i never will. Over all this amp is pretty straight forward and those LDR's are the only funky parts in this amp
Title: Re: Fender Super 60 Volume Problem
Post by: Willabe on May 26, 2011, 08:50:21 am: Oh. That's why you asked about the LDR's for an option for sluckeys warbler?

Brad :icon_biggrin:
Title: Re: Fender Super 60 Volume Problem
Post by: plexi50 on May 26, 2011, 12:09:10 pm: No i was wondering if different LDR's produced a different tonal response. Having done some reading since then i have read that different LDR part numbers do produce different tone in amps. I was uncertain if the VTL5C3 LDR's i ordered would work or what they would sound like in this amp. I still wonder what the 21L915 original part numbered LDR is in reference to as far as data goes

There is nothing online about this part number except for one post that stated the 21L915 was used in the Fender Super 60 and that having tried other LDR's the person said the 21L915 sounded better than the other LDR's he had tried

It works /