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Old 14th January 2011, 01:53 PM   #1
johnm is offline johnm  United Kingdom
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Default Sony TA-F6B PSU repair

Hi folks!

I have a Sony TA-F6B which I recently was given, virtually for free. It's a lovely looking - and by all accounts sounding - amplifier so I'd like to get it working again.

The last owner said it made a loud popping sound one day, and hasn't worked since. After taking the amp apart, it's obvious the owner before him either did some tinkering, or gave it to a tech who cut a few corners...!

I have traced the problem to the PLPS (Pulse Locked Power Supply - basically a late 70s Sony SMPS I think). A heatsink/clamp to four power transistors was not replaced by previous owner/tech so in the end two of these met their maker! Worse he replaced two of the transistors with a different make, and all four are meant to be hFE/batch matched. There is also evidence of lifted solder pads and a jumper wire too in the following pics:

Click the image to open in full size.

Click the image to open in full size.

Here's what it should look like with the missing clamp:

http://picasaweb.google.com/895720/S...51198508682210

So basically, I need to know what an ideal modern substitute for the 'R' hFE grade, and 'O' hFE grade Sanken 2SC2023 power transistor would be please, as the original devices seem next to impossible to get hold of now.

Any help/advice would be gratefully received

Thanks,

- John

Last edited by johnm; 14th January 2011 at 02:14 PM.
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Old 14th January 2011, 03:08 PM   #2
johnm is offline johnm  United Kingdom
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The original specs for this part:

2SC2023 pdf, 2SC2023 description, 2SC2023 datasheets, 2SC2023 view ::: ALLDATASHEET :::
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Old 14th January 2011, 05:27 PM   #3
jaycee is offline jaycee  United Kingdom
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Those transistors with gold leads are bad news... look to replace them.

Fortunately there should be loads of suitable TO-220 transistors now that SMPS are all the rage. Fairchild are probably best to look at for this. The high Vceo and fast(ish, for those days) switching speed will be whats important here.
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Old 14th January 2011, 05:52 PM   #4
jaycee is offline jaycee  United Kingdom
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Actually keeping it simple, TIP50 looks like it will be suitable
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Old 14th January 2011, 05:52 PM   #5
Mooly is offline Mooly  United Kingdom
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What about using something like BUT11AF (plastic insulated TO220) that is common in TV and SMPS use.
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Old 14th January 2011, 05:56 PM   #6
Mooly is offline Mooly  United Kingdom
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Also just to add that 99% of SMPS failures are down to electroylitics developing high ESR (drying out).

It would be a big help to see the circuit... those 2335's were used from memory in the Sony SLC9 and SLC7 VCR PSU's
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Old 14th January 2011, 06:00 PM   #7
Mooly is offline Mooly  United Kingdom
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Free manual here,
Sony | Owners Manuals, Service Manuals, Schematics, Free Download | HiFi Engine
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Old 14th January 2011, 06:03 PM   #8
johnm is offline johnm  United Kingdom
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Thanks for the suggestion guys - much appreciated

I'm really no more than a 'solder by numbers' DIY guy so lack the knowledge about what parts are best to substitute.

The caps on the main board will be replaced with Panasonic and Rubycon 105C long life types (mostly FC/FM and ZLH low esr types).

Here's a scan of the PSU (or PLPS!):

Click the image to open in full size.

Click the image to open in full size.

- John

Last edited by johnm; 14th January 2011 at 06:12 PM.
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Old 14th January 2011, 06:05 PM   #9
johnm is offline johnm  United Kingdom
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Q609-612 are the 2SC2023-O or Rs

Q601 & Q613 (the two on the side that are red in the pictures a few posts above) are the 2SC2023-Rs

- John

Last edited by johnm; 14th January 2011 at 06:14 PM.
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Old 14th January 2011, 06:07 PM   #10
johnm is offline johnm  United Kingdom
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Quote:
Originally Posted by Mooly View Post
Many thanks for that link Mooly but I already have the full service manual which I had to pay to download - the Hi-Fi Engine one is missing many pages.
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