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Re-capping an SX 737

Those readings were done correctly, but they are lousy....

(You don't yet need a better manual to do what's below, to figure out what's needed this weekend)

What's next is to remove the four output transistors and test them according to this thread:
http://www.audiokarma.org/forums/showthread.php?t=43186
and read down to post 11 to get sample results and a reporting format.

Don't put them back, instead insulate the empty sockets so nothing shorts out and turn the amp back on, and retake the readings (20-33) again. The design of the amplifier circuit is of a type that can be turned on and tested without the outputs.

We will continue to do tests without the outputs installed until we have the correct operating conditions established - even to the point of replacing other transistors in the board.

when we are done they will read something like this:
(the measurement points with or without the outputs (almost, without them, e = 0.000) )
20(e)= +0.02
21(b)= +0.6
22(c)= +33.2
23(e)= -0.02
24(b)= -0.6
25(c)= -33.2
 
Thanks for the links EchoWars :thmbsp:

Damn , I guess those readings are messed up :sigh: . This receiver just does not want to cooperate ..... I'll go ahead and pull the transistors . What do you recommend I insulate the holes with ?
 
Maron said:
Thanks for the links EchoWars :thmbsp:

Damn , I guess those readings are messed up :sigh: . This receiver just does not want to cooperate ..... I'll go ahead and pull the transistors . What do you recommend I insulate the holes with ?
Click to expand...

The sockets on the other side of the to-3 (oval shaped) output transistors will be bouncing around loose, those sockets are what should be isolated or insulated - also notice that when they go back together (socket + transistor) there is a LIP on the socket that mates with the heatsink for an exact placement of the socket, and if the two screws are tightened without this lip in it's recess, the sockets can be broken by the force.

The fact that those readings are messed up can be good news, if it turns out to be just the output transistors... then we don't have to mess with the little transistors on the board, just screw in (grease them up first - we'll get to that later) some new ROBUST output transistors and you're good to go, these voltage readings with the output transistors removed will determine that.

BTW: didn't you download the hi-res version of the sx-737 manual in the database? It's about 25 meg...
 
I didn't download the hi-res s/m , it was the standard . Not sure why I didn't , but I have it now , all printed out on heavy paper and put into a binder .

I did not have much time to work on her today , spent most of it at the hospital . Now that I am ready to pull those out , I'm wondering if i need to remove the heatsink to gain access to the screws on the socket of the transistors . I'll look some more once I finish my coffee and wake up . :)
 
Readings with the transistors removed :
20 = -33.7
21 = -32.9
22 = +36.6
23 = -33.7
24 = -35.0
25 = -36.5
26 = -6.0
27 = -7.0
28 = -36.5
29 = -36.5
30 = -6.0
31 = -5.5
32 = +36.5
33 = +36.5

Testing of transistors while removed

Q11 :
black lead to base, red lead to collector, result = OL = No conduction
black lead to base, red lead to emitter, result = OL = No conduction
red lead to base, black lead to collector, result = .481v
red lead to base, black lead to emitter, result = .498v
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction

Q12:
black lead to base, red lead to collector, result = OL = No conduction
black lead to base, red lead to emitter, result = OL = No conduction
red lead to base, black lead to collector, result = .488v
red lead to base, black lead to emitter, result = .501v
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction

Q13:
black lead to base, red lead to collector, result = .477v
black lead to base, red lead to emitter, result = .492v
red lead to base, black lead to collector, result = OL = No conduction
red lead to base, black lead to emitter, result = OL = No conduction
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction

Q14:
black lead to base, red lead to collector, result = .459v
black lead to base, red lead to emitter, result = .487v
red lead to base, black lead to collector, result = OL = No conduction
red lead to base, black lead to emitter, result = OL = No conduction
black lead to emitter, red lead to collector, result = OL = No conduction
red lead to emitter, black lead to collector, result = OL = No conduction
 
Looks like the output transistors are ok, and the problem lies inside the amp.

Like I said before, leave the output transistors out. Can you see the transistor symbols printed on the amplifier board?

Just look at the voltages between the emitter (with the arrow) and the base (what the arrow is pointing to or away from).

When you're fresh, there is no rush, in fact rushing breeds more damage.

BTW- I'm signing off for the night. It's late....
 
Should I take these readings referenced to ground ? Also , would it be worth it to replace/upgrade the output transistors , since we have them out already ? Or should we just hold off on that . My goal is to eventually do a complete overhaul on the receiver . Bring the old girl to like new or better specs/performance .


going to bed ? looks like I am not the only night owl :D
 
Maron said:
Should I take these readings referenced to ground ? Also , would it be worth it to replace/upgrade the output transistors , since we have them out already ? Or should we just hold off on that . My goal is to eventually do a complete overhaul on the receiver . Bring the old girl to like new or better specs/performance .


going to bed ? looks like I am not the only night owl :D
Click to expand...

These readings are done differentially, - not ground referenced:

marktherfixer said:
Here's a neat bit of troubleshooting you could do, read the base to emitter voltages (red dmm probe on base, black dmm probe on emitter) on all of the transistors on the power amp board, if one isn't somewhere around 0.6v, that could be one of the ones that are bad. It's easy, just go by the symbol silk screened onto the board under the component. When you find a bad one, then look up what it is by the number on it and the position on the board.
Click to expand...

New outputs? That's your call if you want to spend $16 extra.... you're spending about $3 for the rest of the amp's transistors, and it won't hurt, if you do all the transistors, then there will be no doubt it's in the best shape.

If you ARE going to replace all the transistors, don't bother with the emitter-base readings.....

So far we can't tell what shape the outputs are in, except they're not shorted or open.

What we do know is there are 8 caps on that board that are old, and since you're working on the amp board already, I will post SOON a list of caps for it, and a few other parts for the protection circuit to do now OR later - but eventually they WILL need doing.
 
Thanks Mark :thmbsp:

I agree , may as well do it while we are working on it . So then caps and all the transistors for the power amp board and parts for the protection circuit . Sounds like a plan . :yes: :scratch2:

Also , what do you think about replacing the pair of big 6800uf 50v caps ?
 
Maron said:
Thanks Mark :thmbsp:

I agree , may as well do it while we are working on it . So then caps and all the transistors for the power amp board and parts for the protection circuit . Sounds like a plan . :yes: :scratch2:

Also , what do you think about replacing the pair of big 6800uf 50v caps ?
Click to expand...

Probably not, if they aren't bulging or have leakage. While we can't measure their capacitance directly, we can infer their condition by:

Measure the DC and AC voltages across the two terminals of each capacitor, and post them, the AC readings will depend upon your meter's internal wiring. We may end up retaking the AC readings with a series capacitor inserted in one test lead.

If the two caps read about the same, and the readings SEEM reasonable, we won't go to the trouble.

Caps die because they loose moisture, they work on a water based chemistry, and the little caps have less to loose. They can be boiled and burst too, by too much voltage or reversed polarity.
 
You can order these from mouser.com:
amp caps:
0.33 25 c1 sx-737 awh-033 pwr-amp-assy 598-DSF050J334 0.33 50 $0.39 polyester film capacitors!!!
0.33 25 c2 sx-737 awh-033 pwr-amp-assy 598-DSF050J334 0.33 50 $0.39 polyester film capacitors!!!
220 6 c7 sx-737 awh-033 pwr-amp-assy 647-UPW1E221MPD 220 25 $0.36
220 6 c8 sx-737 awh-033 pwr-amp-assy 647-UPW1E221MPD 220 25 $0.36
47 35 c9 sx-737 awh-033 pwr-amp-assy 647-UPW1H470MED 47 50 $0.25
47 35 c10 sx-737 awh-033 pwr-amp-assy 647-UPW1H470MED 47 50 $0.25
22 10 c19 sx-737 awh-033 pwr-amp-assy 647-UPW1a220mdd 22 10 $0.11
22 10 c20 sx-737 awh-033 pwr-amp-assy 647-UPW1a220mdd 22 10 $0.11


protection:


two:Q6, Q7 522-ZTX1056A $1.51 ea NPN TO-92E ebc 150v 3a 1w (Vce(sat)=0.3v @ 3a) 120mhz 30-1200 hfe relay driver transistor
one: C6 100uf/16v (100/35) 647-UPW1V101MPD $0.32 protection circuit timing capacitor
one: C5 4.7uf/25v (4.7/50) 647-UPW1H4R7MDD $0.14 protection circuit ac power on signal integrator
two: C1, C2 0.22uf /10v (0.22uf/50v) 598-DSF050J224 $0.52 ea over-current integrators. polyester film capacitors!!!
two: C3, C4 330uf/25v (330/25) 647-UPW1E331MPD $0.37 ea
one: new part 512-1n4004 conventional rectifier 1a 400v $0.07 ea

The other transistors (Q1-Q5) in the protection circuit won't need changing. You are ADDING the 1n4004 diode to increase q7's longevity, every time the relay turns off, the magnetic field's energy has to go somewhere, so it makes a negative voltage pulse that destroys a little bit of the Q7 junction every time, the diode shunts this energy away from the transistor, at the cost of a few MILLISECONDS more time for the relay to disengage...
Pioneer did the diode thing on newer and higher end models as part of the design later on.

edit:
markthefixer said:
We at this point can hopefully trust the power supply and protection board.

I'm kicking myself for not including the amplifier's replacement transistors in the list
primarily because I didn't look, and both the 2sa726's and the 2sc1451's could be trouble.
But since both channels are doing it, I have to find what's in common besides the power supply board.

six: 2sa726 (ecb) > 512-KSA992FBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea
four: 2sc1451 (ebc) > 512-KSC2310YBU to-92 ecb 150v .05a .8w 100mhz 40-240hfe $0.11 ea
two: 2sb527 (bce) > 512-KSA1220AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.39
two: 2sd357 (bce) > 512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40
------- power output transistors -----------
two: 2sb530 > 863-MJ21193G pnp to-3 250v 16A 250W 4mhz 8-75hfe $3.83
two: 2sd370 > 863-MJ21194G npn to-3 250v 16A 250W 4mhz 8-75hfe $3.83
Click to expand...
 
I will get those ordered tonight .

What about the output transistors on the power amp board ? Are those included in there ?
 
Quick question for all the gurus :D . In your experience , would it be worth it to use Black Gate ( if I can find them ) caps or other highly regarded caps . For , lets say , the control amp board or equalizer amp board ( signal path ?) ? ...... To much time on my hands while waiting for parts and the tung oil to dry . lol
So I guess I am having another " while I'm at it " moment . :yes:


BTW .... I forgot to thank you Mark , for the latest parts list . Greatly appreciated !
 
Maron said:
Quick question for all the gurus :D . In your experience , would it be worth it to use Black Gate ( if I can find them ) caps or other highly regarded caps . For , lets say , the control amp board or equalizer amp board ( signal path ?) ? ...... To much time on my hands while waiting for parts and the tung oil to dry . lol
So I guess I am having another " while I'm at it " moment . :yes:


BTW .... I forgot to thank you Mark , for the latest parts list . Greatly appreciated !
Click to expand...

Any possible difference between using Panasonic FC or FM, Nichicon PW or HE or other high quality, high temperature industrial caps and some of the even more expensive but low volume caps out there will be swamped out by the rest of the circuits inside.

Do you know what a multiple sample double blind listening test is? I don't think the difference in a 737 will be detectable under those conditions.

MY opinion is that audio type caps are more hype than physics.
 
Here's something to knock your socks off
(although the formatting doesn't carry over well)
It may be elsewhere on the forum as well - even maybe as an excel file:

uf volts pos model board cap-part# uf volts
220 6 c5 sx-737 awx-071 vol-assy 647-UPW1E221MPD 220 25

1000 50 c7 sx-737 awr-(057,058) pwr-supp 647-upw1h102mhd 1000 50
330 50 c8 sx-737 awr-(057,058) pwr-supp 647-upw1h331mpd 330 50
330 50 c9 sx-737 awr-(057,058) pwr-supp 647-upw1h331mpd 330 50
330 50 c10 sx-737 awr-(057,058) pwr-supp 647-upw1h331mpd 330 50
220 16 c11 sx-737 awr-(057,058) pwr-supp 647-UPW1V221MPD 220 35
220 50 c12 sx-737 awr-(057,058) pwr-supp 647-upw1h221mpd 220 50
100 50 c13 sx-737 awr-(057,058) pwr-supp 647-UPW1H101MPD 100 50
220 16 c16 sx-737 awr-(057,058) pwr-supp 647-UPW1V221MPD 220 35
22 25 c17 sx-737 awr-(057,058) pwr-supp 647-UPW1h220mdd 22 50
100 16 c18 sx-737 awr-(057,058) pwr-supp 647-UPW1E101MED 100 25
100 35 c19 sx-737 awr-(057,058) pwr-supp 647-UPW1H101MPD 100 50

0.22 10 c1 sx-737 awm-025 prot-assy 598-DSF050J224 $0.52 ea 0.22 50 over-current integrators. polyester film capacitors!!!
0.22 10 c2 sx-737 awm-025 prot-assy 598-DSF050J224 $0.52 ea 0.22 50 over-current integrators. polyester film capacitors!!!
330 6 c3 sx-737 awm-025 prot-assy 647-upw1c331mpd 330 16
330 6 c4 sx-737 awm-025 prot-assy 647-upw1c331mpd 330 16
4.7 25 c5 sx-737 awm-025 prot-assy 647-UPW1H4R7MDD 4.7 50
100 16 c6 sx-737 awm-025 prot-assy 647-UPW1E101MED 100 25

0.33 25 c1 sx-737 awh-033 pwr-amp-assy 598-DSF050J334 $0.39 ea 0.33 50 input cap. polyester film capacitors!!!
0.33 25 c2 sx-737 awh-033 pwr-amp-assy 598-DSF050J334 $0.39 ea 0.33 50 input cap. polyester film capacitors!!!
220 6 c7 sx-737 awh-033 pwr-amp-assy 647-UPW1E221MPD 220 25
220 6 c8 sx-737 awh-033 pwr-amp-assy 647-UPW1E221MPD 220 25
47 35 c9 sx-737 awh-033 pwr-amp-assy 647-UPW1H470MED 47 50
47 35 c10 sx-737 awh-033 pwr-amp-assy 647-UPW1H470MED 47 50
22 10 c19 sx-737 awh-033 pwr-amp-assy 647-UPW1a220mdd 22 10
22 10 c20 sx-737 awh-033 pwr-amp-assy 647-UPW1a220mdd 22 10


1 25 c1 sx-737 awg-030 ctl-amp-assy 647-UPW1H010MDD 1 50
1 25 c2 sx-737 awg-030 ctl-amp-assy 647-UPW1H010MDD 1 50
100 16 c5 sx-737 awg-030 ctl-amp-assy 647-UPW1E101MED 100 25
100 16 c6 sx-737 awg-030 ctl-amp-assy 647-UPW1E101MED 100 25
4.7 25 c9 sx-737 awg-030 ctl-amp-assy 647-UPW1H4R7MDD 4.7 50
4.7 25 c10 sx-737 awg-030 ctl-amp-assy 647-UPW1H4R7MDD 4.7 50
4.7 25 c17 sx-737 awg-030 ctl-amp-assy 647-UPW1H4R7MDD 4.7 50
4.7 25 c18 sx-737 awg-030 ctl-amp-assy 647-UPW1H4R7MDD 4.7 50
4.7 25 c19 sx-737 awg-030 ctl-amp-assy 647-UPW1H4R7MDD 4.7 50
4.7 25 c20 sx-737 awg-030 ctl-amp-assy 647-UPW1H4R7MDD 4.7 50
47 10 c21 sx-737 awg-030 ctl-amp-assy 647-UPW1H470MED 47 50
47 10 c22 sx-737 awg-030 ctl-amp-assy 647-UPW1H470MED 47 50
2.2 25 c23 sx-737 awg-030 ctl-amp-assy 647-UPW1H2R2MDD 2.2 50
2.2 25 c24 sx-737 awg-030 ctl-amp-assy 647-UPW1H2R2MDD 2.2 50
100 35 c29 sx-737 awg-030 ctl-amp-assy 647-UPW1H101MPD 100 50

220 35 c2 sx-737 awm-066 mic-amp-assy 647-UPW1V221MPD 220 35
0.47 16 c3 sx-737 awm-066 mic-amp-assy 598-DSF050J474 $0.44 ea 0.47 50 input cap. polyester film
220 6 c6 sx-737 awm-066 mic-amp-assy 647-UPW1E221MPD 220 25
0.47 50 c7 sx-737 awm-066 mic-amp-assy 598-DSF050J474 $0.44 ea 0.47 50 input cap. polyester film

1 25 c1 sx-737 awf-011 eq-amp-assy 647-UPW1H010MDD 1 50
1 25 c2 sx-737 awf-011 eq-amp-assy 647-UPW1H010MDD 1 50
330 6 c7 sx-737 awf-011 eq-amp-assy 647-upw1c331mpd 330 16
330 6 c8 sx-737 awf-011 eq-amp-assy 647-upw1c331mpd 330 16
3.3 25 c11 sx-737 awf-011 eq-amp-assy 647-UPW1H3R3MDD 3.3 50
3.3 25 c12 sx-737 awf-011 eq-amp-assy 647-UPW1H3R3MDD 3.3 50
100 25 c17 sx-737 awf-011 eq-amp-assy 647-UPW1H101MPD 100 50
220 16 c18 sx-737 awf-011 eq-amp-assy 647-UPW1V221MPD 220 25

The tuner is included for completeness, but the caps that are LESS than 1 microfarad should be left alone as a few could disturb the tuner's adjustments. TALK to me if / before doing the tuner - there are pitfalls!!

4.7 25 c25 sx-737 awe-043 tuner-assy 647-UPW1H4R7MDD 4.7 50
10 16 c27 sx-737 awe-043 tuner-assy 647-UPW1H100MDD 10 50
0.47 50 c28 sx-737 awe-043 tuner-assy 647-UVZ1HR47MDD 0.47 50
1 50 c33 sx-737 awe-043 tuner-assy 647-UPW1H010MDD 1 50
0.33 10 c38 sx-737 awe-043 tuner-assy 647-UVZ1HR33MDD 0.33 50
1 10 c39 sx-737 awe-043 tuner-assy 647-UPW1H010MDD 1 50
0.47 10 c40 sx-737 awe-043 tuner-assy 647-UVZ1HR47MDD 0.47 50
0.47 50 c49 sx-737 awe-043 tuner-assy 647-UVZ1HR47MDD 0.47 50
0.47 50 c50 sx-737 awe-043 tuner-assy 647-UVZ1HR47MDD 0.47 50
4.7 25 c58 sx-737 awe-043 tuner-assy 647-UPW1H4R7MDD 4.7 50
47 6 c59 sx-737 awe-043 tuner-assy 647-UPW1H470MED 47 50
10 16 c64 sx-737 awe-043 tuner-assy 647-UPW1H100MDD 10 50
0.1 25 c66 sx-737 awe-043 tuner-assy 647-UVZ1H0R1MDD 0.1 50
220 16 c67 sx-737 awe-043 tuner-assy 647-UPW1E221MPD 220 25
100 16 c68 sx-737 awe-043 tuner-assy 647-UPW1E101MED 100 25

6800 50 chassis
6800 50 chassis
 
LOL .... wow :yikes:
thanks for that :thmbsp:

If you are going to AK fest this year , you are going to have to let me buy you a beer . :yes:
 
Readings taken of rebuilt amp board (AWH033)

The protection relay is still not working , I will get to that board later .

20 = +4.68
21 = +4.68
22 = +36.5
23 = +4.68
24 = +4.68
25 = -35.8
26 = +4.63
27 = +4.63
28 = -35.9
29 = -35.9
30 = +4.63
31 = +4.63
32 = +36.9
33 = +36.9
 
Maron said:
Readings taken of rebuilt amp board (AWH033)

The protection relay is still not working , I will get to that board later .

20 = +4.68
21 = +4.68
22 = +36.5
23 = +4.68
24 = +4.68
25 = -35.8
26 = +4.63
27 = +4.63
28 = -35.9
29 = -35.9
30 = +4.63
31 = +4.63
32 = +36.9
33 = +36.9
Click to expand...

With these readings, the protection wouldn't engage anyway. The two channels are at least doing the same thing now, but +4.6v at the amplifier output is still not a good thing.

I will analyze the transistor layouts and the schematics / pcb layout tomorrow to look for gotcha's in the lead arrangements. D.E.K kinda monopolized my time tonight.
 
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