Kenwood KR-5030 troubleshooting

Hello, first post here. Thanks for the resource!

I recently picked up this Kenwood KR-5030 that had the power switch problem. I sorted that quickly with the help of information from these forums. Thank you.

I'm a bonehead. I was going to check the bias and I stupidly shorted out pin 20 & 23 on the audio board. Don't ask... anyway I'm now trying to sort out what damage I did and correct it.

I need your help if I may.

I replace Q1 thru Q4. I replace Q11 thru Q14. I replaced R25 and R15. All these components were fried. Upon replacement of these components I still have something/s left unresolved. Immeadiatley upon power up it smokes R25. I've found that Q1 and Q2 are shorted again. My diagnosing skills are lackluster and could use some direction on where else I need to investigate for cause.

I can supply any pics or measurements needed.
Any help is appreciated.

Thanks

Welcome to Audio Karma. Before any troubleshooting, have you built yourself a Dim Bulb Tester (DBT). It's pretty much mandatory, and for good reason: http://www.audiokarma.org/forums/showthread.php?t=223061

I don't have a dim bulb device but I do have a variac. Is that sufficient?
Thanks

Can be if it has a current meter that tells you when things are drawing too much, but the fail safe here would be to make a DBT. You have a major short somewhere. I'd be checking all the transistors for that channel, as well as diodes and resistors, if I were you.

ManyMoonsAudio said:

Can be if it has a current meter that tells you when things are drawing too much, but the fail safe here would be to make a DBT.

Click to expand...

Ok, makes sense. Thanks

I do know that if I pull R25 from the circuit the unit will power up and sit there not frying. I can measure voltages in that condition but don't know whether I can rely on any readings with out the resistor in place. The problem seems to be isolated in the channel opposite from where the short took place. Both channels drivers suffered the consequences of the action but now with the visibly destroyed components replaced the continuing problem seems to be on the side opposite of the "incident".

I am under the assumption I can remove the output transistors and be able to troubleshoot without jepordizing them. Is that correct?

It so happens I have my 5030 apart on the bench for the same AC switch issue. So while I have it apart I was going to do a re-build.

I am under the assumption I can remove the output transistors and be able to troubleshoot without jeopardizing them. Is that correct?

Click to expand...

Yes, you can pull the o/p bjt's and measure them as well.
But I would suggest testing (ohmeter) all the bjt's that are still in ckt and compare the reading on the good channel with the bad channel.
You have to have Rm 23,25 in the ckt as they complete the feedback path. ot it will sit at one of the supply rails.

visibly destroyed components replaced the continuing problem seems to be on the side opposite of the "incident"

Click to expand...

Need to measure also, can't see all blown parts visually.
Variac will work as a sub for a dim bulb, but you have to monitor the power drawn and the voltages from the rectifiers and regulators.
Is the PS operational, +/-47V, +/-23V, +14V?

rcs16 said:

It so happens I have my 5030 apart on the bench for the same AC switch issue. So while I have it apart I was going to do a re-build.

Yes, you can pull the o/p bjt's and measure them as well.
But I would suggest testing (ohmeter) all the bjt's that are still in ckt and compare the reading on the good channel with the bad channel.
You have to have Rm 23,25 in the ckt as they complete the feedback path. ot it will sit at one of the supply rails.

Need to measure also, can't see all blown parts visually.
Variac will work as a sub for a dim bulb, but you have to monitor the power drawn and the voltages from the rectifiers and regulators.
Is the PS operational, +/-47V, +/-23V, +14V?

Click to expand...

Thank you for your input.

I will pull the outputs and do my testing in that condition for now. I know the outputs on one channel are shorted and that condition is probably responsible for burning R25 instantainously on startup. The question is why...

I will work with your suggestions and see what I find.

Thanks

Driver and output transistors and two resistors were blown. All is well now.

Thanks

Very good, thx for the update.
I have started putting together a BOM for my Kenwood re-build. Let me know if you are interested and I'll share it.
I'll probably start a thread/post pics, documenting when I am done.

Rick

rcs16 said:

Very good, thx for the update.
I have started putting together a BOM for my Kenwood re-build. Let me know if you are interested and I'll share it.
I'll probably start a thread/post pics, documenting when I am done.

Rick

Click to expand...

Your BOM would be a handy thing to have.

I'll be interested to see your progress.

Thanks Rick.

This is what I have so far

Kenwood KR-5030/5330

Audio (X09-1240-10 B/2) (Power Supply Section)

Cm49,50:10,000uF/50V (ale-pol) 35x80mm 2-pin tab
667-ECE-T1JA183EA (Snap In 18000UF 63V ELECT THA)

Cm52:22u/50V (ale-pol) use 47uF/63-100V
667-EEU-FR1J470 (Aluminum Electrolytic Capacitors - Leaded 63volt 47uF 6.3X11mm LS:2.5mm Bulk Strait)
667-EEU-FR1J470B

Cm53:100u/50V (ale-pol) use 220-470uF/63-100V
667-EEU-FR1J221L (Aluminum Electrolytic Capacitors - Leaded 63volt 220uF 10X25mm LS:5mm Bulk Strait)
667-EEU-FR1J221LB

Cm55:220uF/16V (ale-pol) use 220-470uF/25V
667-EEU-FR1E331 (Aluminum Electrolytic Capacitors - Leaded 25VDC 330uF 8x11mm LS3.5mm )

Cm56:100uF/16V (ale-pol) use 470u/25V
667-EEU-FR1E471YB (Aluminum Electrolytic Capacitors - Leaded 25VDC 470uF 8x15mm LS 5.0mm)

Cm57,58:220uF/35V (ale-pol) use 470uF/35V
667-EEU-FR1V471 (Aluminum Electrolytic Capacitors - Leaded 35VDC 470uF 10x16mm LS5mm)

Dm15:M4C-3 (200V/10A bridge? with heatsink)
512-GBPC2506W Bridge Rectifiers 25A Bridge Rectifier 25x25mm
567-624-60AB (21x21x15mm)

Dm17:WO6B
512-1N4004

Dm18:YZ-140 (14V zener glass 500mW)
512-1N5244B

Dm19,20: WZ-240 (24V zener glass,DO-41)
512-1N4749ATR
512-1N5252B Fairchild 24 V, 0.5W Zener

Qm25:2SC789(Toshiba,70V,4A,30W@25Ccase,hfe=40-240@0.5A,Ft=3MHzmin,TO-220AB,BCE)
512-KSD363YTU (BCE)

Audio (X09-1240-10 A/2) (PREDRIVER)

Cm1,2:22uF/25V (tant-pol) I/P coupling
667-ECQ-V1H225JL (Film Capacitors 2.2uF 50V 5%)

Cm3,4:0.22uF/35V (tant-pol)Sub-filter
667-ECQ-V1H224JL (Film Capacitors .22uF 50V 5%)
555-RFS25V220ME3#5

Cm7,8:47uF/16V (ale-np)
647-UES1E470MPM (Aluminum Electrolytic Capacitors - Leaded 25volts 47uF 85c 10x12.5 5LS)

Cm11,12:1UF/50V (ale-pol) (tone)
667-ECQ-V1H105JL (Film Capacitors 1uF 50V 5%)
555-RFS50V010ME3#5

Cm17,18:10UF/25V (ale-pol)
667-ECQ-V1H225JL (Film Capacitors 2.2uF 50V 5%)
555-RFS35V100ME3#5 (Aluminum Electrolytic Capacitors - Leaded 10uF 35V 20% Audio SILMIC II)

Cm19,20:100uF/10V (ale-pol)

Cm21,22:10uF/25V (ale-pol)

Cm24:330uF/50V (ale-pol,16(D)x35mm) (-47V filter,use 560uF/63V)
667-EEU-FR1J561L

Cm27,28:1uF/50V (ale-pol)
667-EEU-FC1H1R0
555-RFS50V010ME3#5

Cm33:47UF/10V (ale-np)
647-UES1E470MPM (Aluminum Electrolytic Capacitors - Leaded 25volts 47uF 85c 10x12.5 5LS)

Cm34:100uF/25V
667-EEU-FC1J101

Q1,3:2SC2261(O)(y) (Sanken,80W,TO-3)
Q2,3:2SA981(O)(Y) (Sanken,80W,TO-3)
TO-3 micas (Need a total of 4): 534-4636, 534-4667, 534-4636

Dm1,2,5,6,9,10:1S2076,1S1555 (100mA,35V,DO-35)
512-1N4148TA

Dm3,4:STV-4HG

Dm8,16,17:WO6B (DO-41,Glass)
512-1N4004

Dm11:1S2076A (35V,150mA,250mW,trr=8ns,C=3pF,DO-35)
512-1N4148TA

Qm1~4:2SA750(1)(E) (TO-92,ecb)
512-KSA992FTA (Vce=120V,Ic=50mA,Pd=500mW,Ft=100M,hfe=300-600,TO-92,ecb)
2SA1083,2SA1034(D)(E)

Qm5~8:2SC1775A(E)(F) (Vce=120V,Ic=50mA,Pd=300mW,Ft=120M,hfe=400-1200,TO-92,ECB)
512-KSC1845FTA (Vce=120V,Ic=50mA,Pd=500mW,hfe=400-1200,Ft=110M,TO-92,ECB)
512-KSC2316YTA (Vce=120V,Ic=800mA,Pd=900mW,hfe=120-240,Ft=120M,TO-92L)

Qm9,10:2SA872A(E)(F) (Vce=120V,Ic=50mA,Pd=300mW,Ft=120M,hfe=400-1200,TO-92,ECB)
512-KSA992FTA (Vce=120V,Ic=50mA,Pd=500mW,Ft=100M,hfe=300-600,TO-92,ecb)
512-KSA916YTA (Vce=120,Ic=800mA,Pd=900mW,Ft=120M,hfe=120-240,TO-92L)

Qm11,12:2SD600K(E)(F)/2SC1567A(Q)(R) (TO-126,ECB)
512-KSC2690AYS (NPN,Ic=1.2A,Vce=160V,Pd=1.5W,Ft=155M,hfe=160-320,TO-126ML,ECB)
863-2SC3902S (NPN,Ic=1.5A,Vce=160V,Pd=1.5W,Ft=120M,hfe=140-280,TO-126ML,ECB)

Qm13,14:2SB631J(e)(F)/2SA794(Q)(R) (TO-126,ECB)
512-KSA1220AYS (PNP,Ic=1.2A,Vce=160V,Pd=1.5W,Ft=155M,hfe=160-320,TO-126ML,ECB)
863-2SA1507S (PNP,Ic=1.5A,Vce=160V,Pd=1.5W,Ft=120M,hfe=140-280,TO-126ML,ECB)

Qm19,20:2SC1890A(E)(F) (Vce=120V,Ic=50mA,Pd=250mW,hfe=400-1200,Ft=200M,TO-92,ECB)
512-KSC1845FTA (Vce=120V,Ic=50mA,Pd=500mW,hfe=400-1200,Ft=110M,TO-92,ECB)

Qm21:2SC945(Q)(R) (Vce=50V,Ic=150mA,Pd=250mW,hfe=400-270,Ft=250M,TO-92,ECB)
512-KSC945CYTA (Vce=50V,Ic=150mA,Pd=250mW,hfe=400-270,Ft=300M,TO-92,ECB)
512-KSD1616AGBU

Qm22,24:2SA733(Q)(R) (Vce=50V,Ic=50mA,Pd=300mW,hfe=250-1200,Ft=180M,TO-92,ECB)
512-KSA733CYTA (Vce=50V,Ic=150mA,Pd=250mW,hfe=120-240,Ft=180M,TO-92,ECB)

Qm23:2SC1735(E) (Vce=100V,Ic=500mA,Pd=800mW,Ft=120M,hfe=150-300,TO-92-L,BCE)
512-KSC2316YTA (Vce=120V,Ic=800mA,Pd=900mW,Ft=120M,hfe=120-240,TO-92L,ECB)

VR1,2:500ohm pot
652-3309P-1-501

Tuner(X05-1480-10 A/4)
Cg22:47u/50V(ale-pol,dc filter)

Cg25:1u/50V(ale-pol,dc filter)

Cg22:47u/50V(ale-pol,dc filter)

Cg49:220u/16V(ale-pol,dc filter)

Cg85,86:3.3uF/10V(tant-pol,sig coupling for phono i/p)
667-ECQ-V1H225JL (Film Capacitors 2.2uF 50V 5%)

Cg87,88:47uF/50V(ale-pol,sig coupling,sig coupling for phono feedback)
555-RFS35V470MH3#5 (Aluminum Electrolytic Capacitors - Leaded 47uF 35V 20% Audio SILMIC II)

Cg97,98:4.7uF/50V(ale-pol,sig coupling,sig coupling for phono o/p)
667-ECQ-V1H225JL (Film Capacitors 2.2uF 50V 5%)

667-ECQ-U2A103ML (Use across the AC switch terminals)
667-ECQ-U3A103MG