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F4 power amplifier
F4 power amplifier
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Old 25th August 2018, 10:36 PM   #4411
6L6 is offline 6L6  United States
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F4 power amplifier
They are 28yr old. (9016 and 9006 date codes)

What's wrong with the caps already installed?
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Old 25th August 2018, 10:49 PM   #4412
Zen Mod is offline Zen Mod  Serbia
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F4 power amplifier
maybe already installed are 48yrs old ?

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Old 26th August 2018, 05:28 PM   #4413
albertli is offline albertli  Canada
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Quote:
Originally Posted by 6L6 View Post
They are 28yr old. (9016 and 9006 date codes)

What's wrong with the caps already installed?
Jim,
Nothing wrong with the existing caps but just query if this freeby will give better result. Oh. I know now they are too old the the job. Will give them back.
Thanks
Albert
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Old 26th August 2018, 05:31 PM   #4414
albertli is offline albertli  Canada
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Quote:
Originally Posted by Zen Mod View Post
maybe already installed are 48yrs old ?

Choky,
At least not as old as I'm.
Albert
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Old 26th August 2018, 05:39 PM   #4415
Zen Mod is offline Zen Mod  Serbia
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same here

one thing is if they're old , other thing is are they tired and worn and dry

try reforming them - just slab them to highest possible DC PSU you have (up to declared voltage) through 100K resistor and leave them connected that way for few days

then try them , nothing wrong with some testing fun

if you have a place in case , connect 50uF motor-run caps as bypass for final caps in filter section , that usually brings some speed and freshness

look at surplus places , sometimes you can find bargains
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Old 27th August 2018, 07:15 AM   #4416
albertli is offline albertli  Canada
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Quote:
Originally Posted by Zen Mod View Post
same here

one thing is if they're old , other thing is are they tired and worn and dry

try reforming them - just slab them to highest possible DC PSU you have (up to declared voltage) through 100K resistor and leave them connected that way for few days

then try them , nothing wrong with some testing fun

if you have a place in case , connect 50uF motor-run caps as bypass for final caps in filter section , that usually brings some speed and freshness

look at surplus places , sometimes you can find bargains
Thanks choky,
You said there might be chance to wake them up by charging them with the stated maximum voltage and series a 100k from the PSU.
I have a bench PSU with adjustable dual 25v. I'll try series both supplies and tune to the cap maximum voltage to try.
Thanks for the advice
Albert
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Old 7th November 2018, 04:20 PM   #4417
Pocoyo is offline Pocoyo  Indonesia
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Hi Zen Master ...

Just a little question, if i use jt-123-alch for input F4 (and i
hope to get bigger sound) so i need to connect output transformer
to input F4 (R1 1k) with / without change the schematic ?

If there is a change, can you let me know ... What is the part
need to change, move, connect or cut?

My input is unbalance / rca

Thank u before
Regards, jeffry
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Old 7th November 2018, 06:04 PM   #4418
Zen Mod is offline Zen Mod  Serbia
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clarify "R1 1K"

good to point to your reference schm , also to say which source/preamp you're using
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Old 7th November 2018, 07:12 PM   #4419
Itsmee is offline Itsmee  England
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R1 in F4 r0.

Nice idea, something I intended to try at some stage... some day, when I've cleared my backlog of projects.

ZM will correct me if Im wrong, I'm not sure if it will drive the mosfets directly (3deep, maybe, 6 deep, don't know), but I would try inserting the transformer between R3,R4 and C1,C2.

Wire as autoformer, ground pin 8, drive pin 7, link 6&7, 4&5, 2&3, take output from pin 1.

Edit. You could then delete R24 R25 C3 & C4.

You may have to play with the transformer output loading.

Last edited by Itsmee; 7th November 2018 at 07:41 PM.
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Old 9th November 2018, 10:34 AM   #4420
Pocoyo is offline Pocoyo  Indonesia
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Default Input/output transformer

Thanks a lot Zen, Can you give me a little enlightment about

If we look for jt-123-flpch or lundahl lundahl oleh 1690 they ratio
are 1+1:1+1 so these mean 1 input will 2x output ?

So if i look on lundahl series ll 1676 and ll 1677 they ratio were
1+1:2+2 and 1+1:4+4 so if Will 4x output and 8x output ?

Can we use 1pcs ll 1676 with ratio 1+1:2+2 for balance input?
So we will get 2x output for every input?

Pls correct me if im wrong

Thank you Zen, br
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