Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: electroern on May 02, 2020, 01:25:38 pm

Title: Hoffman Chassis No.1129 Filter cap can repair question
Post by: electroern on May 02, 2020, 01:25:38 pm
Hello folks, hope you all find yourselves well.

I need some advice about replacing the can caps in my Hoffman amp.

There are two cans that need to be replaced but I’m wondering if it’s alright to slightly increase the uF values of those caps. One can is an 80uf/80uf at 350WV which I would like to replace with a 100uf/100uf at 450WV. Would this be ok? And the second can is a 40uf 350Wv/ 40uf 350WV/ 50uF 25WV/ 50uF 25WV which I would like to replace with a 50/50/50/50uf 350WV CE can cap. Any help would be greatly appreciated.

Thank you kindly,
ElectroErn
Title: Re: Hoffman Chassis No.1129 Filter cap can repair question
Post by: sluckey on May 02, 2020, 01:41:22 pm
That's OK
Title: Re: Hoffman Chassis No.1129 Filter cap can repair question
Post by: EL34 on May 02, 2020, 02:42:51 pm
Quote from: electroern on May 02, 2020, 01:25:38 pm
Hello folks, hope you all find yourselves well.

I need some advice about replacing the can caps in my Hoffman amp.

There are two cans that need to be replaced but I’m wondering if it’s alright to slightly increase the uF values of those caps. One can is an 80uf/80uf at 350WV which I would like to replace with a 100uf/100uf at 450WV. Would this be ok? And the second can is a 40uf 350Wv/ 40uf 350WV/ 50uF 25WV/ 50uF 25WV which I would like to replace with a 50/50/50/50uf 350WV CE can cap. Any help would be greatly appreciated.

Thank you kindly,
ElectroErn

Must be another Hoffman?
I never used any caps like that
Title: Re: Hoffman Chassis No.1129 Filter cap can repair question
Post by: electroern on May 02, 2020, 04:12:22 pm
It’s from a Hoffman model 8006 console circa 1959
Title: Re: Hoffman Chassis No.1129 Filter cap can repair question
Post by: PRR on May 03, 2020, 12:52:04 am
> Hoffman model 8006 console circa 1959

The Hoffman who runs this place was a wee lad in 1959.

You have a console from Hoffman Radio/TV/Hi-Fi out in Los Angeles. Some of these were very nice machines. Details and schematics are hard to find.

What is the tube line-up?

However I am inclined to say "do it". Old e-caps had wide tolerances. An "80uFd" could be 120uFd or more. A modern "100uFd" is not likely to be over 110uFd.
Title: Re: Hoffman Chassis No.1129 Filter cap can repair question
Post by: PRR on May 03, 2020, 01:01:50 am
Some info:
https://www.radiomuseum.org/r/hoffman_sp807_ch_1129.html

The 7189 can, in THIS chassis, be subbed with EL84/6BQ5. (Most 7189 amps take advantage of the 7189's higher ratings, this one does not.)

Partial schematic: