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Hoffman Amps Forum image Author Topic: Making progress on my AB763 build - Filter Cap Question  (Read 2441 times)

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Offline Hazcat

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Making progress on my AB763 build - Filter Cap Question
« on: December 22, 2021, 02:20:12 pm »
I'm making progress on my AB763 build - I'm building the One Channel version, adding dwell, presence and master volume per robrob's guidance. 
I'll post some pics after this Christmas bustle, but I have one quick question right now - I'm building a Deluxe, but I bought 22mfd filters rather than the 16's that are called for in the Deluxe - I missed that distinction when I made my AB763 BOM order.  Is that added capacitance going to give me problems or affect tone?  I understand the basics of tube theory, but I've read a lot posts here, robrob and Aiken that bring up finer points that I had never considered (self-taught technician, here). Now I'm kind of gun-shy about changes. I know the GZ34 can provide the current, but my Hammond PT is rated at 660VCT @ 138mA. Is there a rule of thumb for supply current increase with capacitance?  The schematic calls for 5 x 16mfd (1st two are parallel).

Edit Subject line... sluckey
« Last Edit: December 23, 2021, 03:06:28 pm by sluckey »
1948 Magnatone Melodier M-195-4-J, 1956 Silvertone 1333,
1963 Epiphone Electra EA-26-RVT
AB763-1 in the oven.....

Offline pdf64

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Re: Making progress on my AB765 build - Filter Cap Question
« Reply #1 on: December 22, 2021, 02:28:20 pm »
When I started buying high voltage caps in the 80s, electrolytic types had a +100% to -50% tolerance. So 16 nominal might be anywhere between 8 and 32, 22 nominal 11 - 44.
There’s quite a lot of overlap.
I wouldn’t worry about it.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him! BBC News feature  https://www.bbc.co.uk/news/articles/cm26llp

Offline dwinstonwood

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Re: Making progress on my AB765 build - Filter Cap Question
« Reply #2 on: December 22, 2021, 02:39:35 pm »
Nice build! I'm working on a 6G3 rebuild and I intentionally upped the 16uF's to 22uF's.
I'm guessing you just haven't added wires between pins 2 and 7 on the two power tube sockets yet, but will.

Offline shooter

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Re: Making progress on my AB765 build - Filter Cap Question
« Reply #3 on: December 22, 2021, 03:23:36 pm »
Quote
When I started buying high voltage caps in the 80s,
about 10 years ago I got notice that I was/could be in a class action lawsuit because I was buying caps in the 80's/90's.
I ticked the ya sure box, 2 years later I got an 87cent check!   :laugh:   I coulda had actual dollars but couldn't provide receipts for about 80% of the buys I did.   Believe it was a "price gouge" suit, somewhere FarEast of America
Went Class C for efficiency

Offline 66Strat

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Re: Making progress on my AB765 build - Filter Cap Question
« Reply #4 on: December 22, 2021, 08:07:39 pm »
Quote
When I started buying high voltage caps in the 80s,
about 10 years ago I got notice that I was/could be in a class action lawsuit because I was buying caps in the 80's/90's.
I ticked the ya sure box, 2 years later I got an 87cent check!
   :laugh:   I coulda had actual dollars but couldn't provide receipts for about 80% of the buys I did.   Believe it was a "price gouge" suit, somewhere FarEast of America

LRF lawsuit (Lawyer Relief Fund) :l2:
Regards,
JT

Offline TigerTrading2021

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Re: Making progress on my AB765 build - Filter Cap Question
« Reply #5 on: December 23, 2021, 02:52:01 pm »
Quote
When I started buying high voltage caps in the 80s,
about 10 years ago I got notice that I was/could be in a class action lawsuit because I was buying caps in the 80's/90's.
I ticked the ya sure box, 2 years later I got an 87cent check!   :laugh:   I coulda had actual dollars but couldn't provide receipts for about 80% of the buys I did.   Believe it was a "price gouge" suit, somewhere FarEast of America

Looking for things I could buy with 87Cents ummm ummm yep Nothing Lmao
I remember that lawsuit I got notice as well but never followed up dang I might could of got like 55Cents that half a dang candybar.

Offline mresistor

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Re: Making progress on my AB763 build - Filter Cap Question
« Reply #6 on: December 24, 2021, 01:29:39 pm »
Hi, if it were me I would wire up the board to sockets pots jacks etc  before installing components. Nice work so far hope she fires up fine first time.


I've built several DRs one and two channels and repaired vintage amps in my time and I have not perceived any difference in 16uf filters vs 20 or 22uf filters. 
« Last Edit: December 24, 2021, 02:06:20 pm by mresistor »

Offline Willabe

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Re: Making progress on my AB763 build - Filter Cap Question
« Reply #7 on: December 24, 2021, 11:30:23 pm »
Hi, if it were me I would wire up the board to sockets pots jacks etc  before installing components.

Why?

Fender and others always filled the eyelet/turret board 1st and had fly leads on the board to make the connections to the pots, tube sockets, etc. after installing the already populated board.

It's faster and easier to populate the board outside of the chassis. More room to move outside the chassis.   

 


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