Pioneer sx-636...could use some help

[randallflag]

Yes, adjustment after work.

Also, didn't see it mentioned, heat sink compound should be NON-conductive, some are ("arctic silver") and we have seen some delayed (go figure.. ) ill effects when they finally short out.

I got the basic radioshack heatsink silicone based compound. I avoided anything that had arctic silver on it.

 

[randallflag]

Update!

No super pretty but I think I did ok, ran it pretty hard for awhile and haven't had any heat issues as of yet so I'm gonna leave the amp section alone now. To re-iterate for anyone following, as per pioneer god aka markthefixer's part list I can personally confirm his precise format and component choices were perfect replacements for the original components.

(AWH-034-0)
Q1(2sa726)--512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe
Q2(2sa726)--512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe
Q3(2sa726)--512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe
Q4(2sa726)--512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe

Q5(2sc1451)--512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe
Q6(2sc1451)--512-KSC3503estu to-126 ecb 300v .1a 1.2/7w 150mhz 40-320hfe

Q7(2sc1509)--512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe
Q8(2sc1509)--512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe

Q9(2sa777) --512-KSA1220AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe
Q10(2sa777)--512-KSA1220AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe

Q11(2sd371)--863-MJ21194G npn to-3 250v 16/30A 250W 8-75hfe 4mhz ?
Q12(2sd371)--863-MJ21194G npn to-3 250v 16/30A 250W 8-75hfe 4mhz ?

Q13(2sb531)--863-MJ21193G pnp to-3 250v 16/30A 250W 8-75hfe 4mhz ?
Q14(2sb531)--863-MJ21193G pnp to-3 250v 16/30A 250W 8-75hfe 4mhz ?

Caps:
awh-034 c1 0.33 25 cssa 0.33 50 598-DSF050J334
awh-034 c2 0.33 25 cssa 0.33 50 598-DSF050J334
awh-034 c7 220 6 cea 220 10 647-UPW1A221MED
awh-034 c8 220 6 cea 220 10 647-UPW1A221MED
awh-034 c9 47 35 cea 47 35 647-UPW1V470MED1TD
awh-034 c10 47 35 cea 47 35 647-UPW1V470MED1TD

Moving on to the EQ amp assembly, I forgot to take photo's of the before. I did however make sure to do one component at a time this time around and double check positioning, polarity(when needed) before moving on to the next. Takes a little longer but definitely feel more confident after its done as everything has already been checked twice.

To recap on the EQ amp section the following is the list I threw together when researching the parts replacement. Vetted by markthefixer I didn't have any problems although some slight changes.

C1 and C2 link were out of stock at the time I ordered(in stock now) so I ordered a similar capacitor with the same specs. I can't remember the exact model at this time...oh well. I also followed his advice for C5 and C6( 647-UPW1V101MPD) and C13 and C14(667-ECQ-V1H474JL). The C13 and C14 parts were large enough he's right on that the ones I originally choose probably would not have fit :thmbsp: On a side note the 4 clear plastic components on the front of the board(see photo) had me a little concerned especially when having to solder other components close to their leads. What are those? And am I correct in needing to be careful around them...dunno, plastic makes me nervous?

AWE-014-0 EQ Amp Assembly

Transistors

Q1+Q2+Q3+Q4, Transistor, 512-KSC1845FTA
http://www.mouser.com/ProductDetail/...TsDnxfJvPSY=

Caps

C1+C2, 647-UKL1H3R3MDD1TA
http://www.mouser.com/ProductDetail/...%2biHeHMk=


C3+C4, 667-ECQ-E1474KF
http://www.mouser.com/ProductDetail/...SWXvGm01zmE=

C5+C6, 647-UPW1V101MPD1TD on order, this is more appropriate for the future too: use 647-UPW1V101MPD
http://www.mouser.com/ProductDetail/...b4DY20Ew==

C11+C12, 647-UKL1C220KDDANATA (They did not have 10v in stock when I searched so I went 16v)
http://www.mouser.com/ProductDetail/...ccX9kNexCTY=

C13+C14, 667-ECQ-E1474KF these are 100v parts and you could have a hard time getting them into the available space, 50v parts 667-ECQ-V1H474JL would be a better fit.
http://www.mouser.com/ProductDetail/...SWXvGm01zmE=

Moving on to the control board. Haven't actually done any work on it yet. At first glance I figured it was going to be a pain in the ___ to get access but actually ending up being pretty easy. 6 screws in the face section, some adjusting of the connected wires and she slides right out, nice. Actually this whole unit has been pretty easy to access so far.

 

[JT-3]

Fantastic thread, very helpful.

 

[randallflag]

Update!!!

Dohhhh!!!! While getting my parts laid out for the (awk-035-0) control board I realized that I was short on 512-KSA992FBU's, fearing first that I had been shorted by mouser I realized quite quickly that I simply hadn't ordered enough...in fact I was 4 short as I didn't have a couple for the tuner board as well...:withstpd:. Rookie mistake I guess oh well. Since I'm this far into this unit its too late to turn back, I've already spent more than the worth of the unit :yes:...and frankly I don't care If i'm gonna place another order I figure lets finish this off completely.

markthefixer we never discussed the power supply circuit, I have put together a list in a format you recomended.

(AWR-60-0) Power Supply Circuit

awr-60 c6 470 50 cea 470 50 647-UPW1H471MHD
awr-60 c7 220 50 cea 220 50 647-UPW1H221MPD
awr-60 c8 220 50 cea 220 50 647-UPW1H221MPD
awr-60 c9 100 50 cea 100 50 647-UPW1H101MPD
awr-60 c11 100 16 cea 100 16 647-UPW1C101MED
awr-60 c12 220 16 cea 220 16 647-UPW1C221MPD
awr-60 c13 10 35 cea 10 35 647-UPW1V100MDD
awr-60 c14 220 50 cea 220 50 647-UPW1H221MPD

(ACH-041-0)

2 x 6800uf 35v these are the 2 large black caps in the photo's. Are these even replaceable? I feel like I've read somewhere about leaving them in place but soldering in smaller replacements on the leads underneath. Any insight from those following would be appreciated as i'm almost to the finish line with this.

 

[markthefixer]

They can be replaced, the mountings and lead spacings / mechanical details of the connections will predominate your considerations.

power supplies routinely get new transistors...

you'll do fine with ksc2073(x2) and ksd1616 transistors.

the smaller caps underneath are 2.2uf 100v stacked film caps for bypassing purposes.

 

[randallflag]

They can be replaced, the mountings and lead spacings / mechanical details of the connections will predominate your considerations.

power supplies routinely get new transistors...

you'll do fine with ksc2073(x2) and ksd1616 transistors.

the smaller caps underneath are 2.2uf 100v stacked film caps for bypassing purposes.

Thanks mark parts are on the way. While waiting for them I have a question about setting the bias on the amp section. I followed the instructions in the manual(aux setting,8ohm dummy load on A speakers) took my readings at the appropriate pins on the amp board and adjusted the pots to achieve a 20mv reading as stated in the manual. My question is this....with the newer components is 20mv still valid? Frankly to me the amp sounds weak and slightly distorted at the 20mv setting. My ears were inclined to like a setting of at least 25mv. Is this uncommon?

 

[randallflag]

Anyone?

 

[markthefixer]

after a certain idle current, all that happens is that there is more heat dissipated - there is no further distortion reduction

BUT if that idle current point has moved THAT high, there could be other problems shifting it there. And to have the shift happen on BOTH channels...

yes

 

[randallflag]

Hmmm, I'll give it another listen, if I remember correctly with the amp board pots minimized all the way left the lowest it would go is 19mv, is that strange? I dunno, other than the settings in the manual should I be setting bass,treble,volume at minimum or does none of that effect the reading?

 

[markthefixer]

idle current is done with NO sound.

 

[randallflag]

after a certain idle current, all that happens is that there is more heat dissipated - there is no further distortion reduction

BUT if that idle current point has moved THAT high, there could be other problems shifting it there. And to have the shift happen on BOTH channels...

yes

Gave it another try early last night after I finished the powersupply circuit. Perhaps I was just tired the night before and the acoustics in my basement shop are horrible anyways. Both holding steady at 20.5 mv and sounds pretty darn good for a little amp. I'll have some pictures up later tonight. Only one last thing to do that I wanted to check with you first. I did pick up some 2.2uf 100v film caps for bypassing. Perhaps a stupid question but do I literally just solder them across the leads of each of the power filter caps?

 

[randallflag]

Update!!

Control board finished. Actually this picture is before I was completely done. The two transistors with the white dots on them have now been replaced with 992's.

Tuner board done, you can see the film caps at the top and also replaced the 2 transistors directly below them per marks advice. Hated seeing those lil'blue sanyo's left in there but i'm guessing mark didn't want those replaced for alignment reasons and I'm not prepared to spend any more on this unit.

Power Supply Circuit was probably the trickiest board to access and work on for me. I didn't have to disassemble anything really but to work on it had to balance the unit on the face, dunno was kinda awkward getting in there but worked out. All caps replaced as well as the transistors. My generated list worked as well as the transistors recommended by mark. I did find one service manual flaw shown below that folks should be aware of.

This cap nestled between the two transistors is stated to be electrolytic in the manual. Weird thing is that on the schematic it shows it as a 220uf50v electro not unlike the similar component sitting next to another transistor on the board. However on the foil side schematic its listed as a 100p ceramic. Also listed as a 220uf 50v in the parts list. I left it alone and is another shining example of the golden rule of "look at the damn board thoroughly before ordering".

I didn't make any attempts to replace the 2 power filter caps, nor did I bypass with them with the film caps as I wasn't sure exactly what I had to do. Fiddled some more with the bias and managed to get it to dead on 20 mv, +-.1 and it sounds pretty darn good for 25wpc. As of now its finally off the bench and i'm enjoying some Miles Davis in my bedroom. I currently have a pair of 40w cs-66g's hooked up to it and it sounds decent. I'm open to suggestions for finding suitable speakers for this little guy, do you think that my 66g's are too much for it?

Anyways thanks for all the advice from all who contributed especially mark as I couldn't have saved this lil guy without your help, your a gentleman and a scholar. :thmbsp:

 

[Alienz]

Congrats and thanks for the good pics! :thmbsp: