2270 no power

Hyperion has recommended a BC337 sub over on the Sansui forum recently. And I see Pete just made a recommendation as well. Looks like the main difference is the BC337 has a lower fT than the original (100MHz vs 300MHz) whereas the PN2222ATA is equal at 300MHz. I don't know if the speed is critical at that position so will defer to Pete's recommendation.

Original SC735:
http://www.datasheetspdf.com/PDF/2SC735/613419/1

Fairchild PN2222ATA:
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/PN2222ATA/

Either way the replacements have a center base pinout and will need some lead bending to fit. The original was center collector.
 
i looked at the bc337 and that is why i chose the other one . but i didn't check all parameters . just voltage current and ft .
hfe really needs checking too
 
Going back to post # 49 I asked if 2N3904 would be a suitable replacement for the one transistor ( 2SC735 ) that tested bad but never did get a response.

I rechecked my thread (it's been a while) and I found that I had replaced H754/H755 (2SC735) with 2N3904
and it is still working fine to date

In this thread, blhagstrom recommends a BC635. so looks like you have multiple options.

http://audiokarma.org/forums/index.php?threads/marantz-300dc-problem.615247/page-2#post-8149318
 
The 25 series of the BC337 covers the hfe range just fine as does the PN2222ATA. The 2N3904 sacrifices IC showing a continuous collector current of 200ma vs 400ma on the original but everything else is in line. Looks like each option has at least one sacrifice. Wish I understood the circuits better to know which sacrifices were appropriate.

:lurk:
 
So many options. I'm not experienced enough to say either way so I will go with the PN2222ATA that Pete suggested. Thanks so much for all the suggestions.
 
It’s been a while since I started this thread and due to uncontrollable circumstances I haven’t been able to devote much time to the repair /restoration of this 2270. I did manage to recap the PS and a little work on the R/S amp board with the gracious help and guidance of Bob ( wlhd1610 ). I replaced H755 -2SC735 with a PN2222ATA as suggested by Pete. The DC offset when checked on the R/S amp was -31.43 V which indicated a problem and the L/S amp was 0.004 . Just yesterday I found that H766 is toast as well on the R/S and will need to be replaced. I do have a few 2N3906 transistors but would I be correct to assume I can’t use it because it would NOT be complimentary to PN2222ATA that’s in place at H755?? I guess the only way I could use it ,is if H755 was a 2N3904 ( that I don’t have ) correct?
 
This is the first unit I've left unfinished for various reasons but I'm now moving forward with it. I have most boards recapped and I'm on the 500 FM detector board and I just noticed an Axial cap at C510. Should I replace it with the same or install a radial cap in that position.
 
What does the board pictorial in the service manual show?
(btw,my 102℉ fever has subsided so I'll be back to help you shortly)

Bob
 
Glad to hear your finally feeling better Bob. The SM shows a axial 50V 1uF. I had a radial at that value so I installed that. DBT was ok. Oh BTW I have sound through the headphones on FM and Aux using my phone as a source.
 

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So should I replace the radial I put in this location with the proper Axial. Will the radial do any harm? I can always replace it when I place my next parts order but that may not be for a bit.
 
Ok thanks Bassblaster. I just wanted to make sure before going any further and forget all about it ,and not get back to it.
 
Following a cap list that was posted on here and on the Phono 700 board at C713 the SM has the cap listed at 50V 100 uF and that is what I just removed,however the cap list has it at 50V 220uF and that was what I ordered but didn't realize it till now. So is the increase in capacitance intentional or a mistake. I would guess to replace with like value especially where uF is specified. Not sure if I have an extra kicking around at that value.
 
That 220 is fine. C713 is the local dc filter and can be increased vs original.
 
Ok thanks Mike. It's funny that you should reply as your thread " 2270 Extreme makeover " was the thread I was reading last night just after I posted. Very interesting thread by the way. I didn't finish that board last night because I worked late and only got that one cap and started to get very sleepy. Thought best to not go any further but I remember having more questions and will check back later. It's off to work I go. Damn shift work. I'm getting way too old for this.
 
That seems like ages ago but glad it's still a good reference. I've never done another like that. I just can't hear a difference when changing resistors.
 
Referring to the 700 Phono board

The cap list I'm using ( don't remember whose list it was ) also has NPN transistors ( ZTX694B ) as replacements for the 458's at H 705/706. I read a lot about KSC1845FTA replacing the 458's so which is best? The 1845 just needs to be turned around whereas the 694 has a different pin out and leads would need some fancy bending.
Also would the ECQ -E2105KF 250DC 1uF film caps on this list be replacing the glass/silver caps at C709/710/711/712 would you suppose?

Reading your rebuild back then you had H707/708 replaced with 1N4148 diodes however again this cap list has that replacement part number at 1N4448. Wondering if I would be good with the 1N4448 that I just installed at those locations?
 
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I don't know anything about the ztx transistors but the 1845's are fine. 709-712 should be polystyrene caps and will not need replacement. The 1uf Panasonic films might be to replace the .47uf films at 701/702 & 714/715.

For the diodes, I don't usually use 4448 but from what I understand they're fairly interchangeable.
 
Thanks Mike.
I used the diodes and changed out the two transistors for now but will wait for someone to help out about the other caps at whatever locations they should go.
 
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