Pioneer SX-950 wont come out of protection

[1MEGΩ]

I am going to give mouser a try with a bulk order.
The part # you gave is for a 1 Mohm trim pot.
I am a novice but the oem pot was a 10k ohm

The 2 part numbers I gave you......Mouser: 652-3296P-1-101LF (100 ohm) and
Mouser: 652-3296P-1-103LF (10,000 ohm) are an exact fit. I have used them on the SX-850 and SX-950 many times.


I would think the place in Alberta would have these pots or can order them for you.

 

[CavScout]

The local places here don’t have them and they say they can get the ones I need in 3 weeks.
Mouser.ca says I will have to pay $20 in import fees PLUS $8 shipping.......for a $6 order

 

[kevzep]

If you get the right parts, you will have no trouble, messing around with parts which are not correct or sub standard are a waste of time.
Sometimes you just have to pay the money to make things right.
I live at the bottom of the world, I order everything from Mouser, sometimes I miss something, and then I have to wait another week to get it as it takes 3-5 working days to get here. I might pay extra but its worth it to do a proper job
The SX950 is a high quality piece of equipment and deserves to have the right parts put into it.
If you continue with the way you are going, it's not going to be a good repair and it may fail again and cause even more damage.

 

[rcs16]

531-PT10H-100 is 100 ohms. It is probably better than the originally spec'd part. if the Bourns parts fit properly go for it.

Mouser.ca says I will have to pay $20 in import fees PLUS $8 shipping.......for a $6 order

I always fill by Mouser order with >=$100 CDN (it is not hard to do) and get next day or following day free shipping to my door, it is fantastic service. Digi-key is the same. I am sure kevzep would love to have this service we are fortunate to have in Canada. A full re-cap, semi replacement will get you over 100 quite easy.
never hurts to have some spare components on hand.
From what I have read here you have issues for which you need to have some spare parts on hand to fix your issues. Ohm out all the resistors, diodes, bjts before you order parts
Do you need a list?
For the amp bjts, ksa992f, ksc3502, ksa1381, KSB596Y, KSD526Y and the o/p's if needed MJ211 93/94 or 95/96, TO-3 micas, paste. I always order min 10 of bjts/diodes/resistors/ecaps to get the next tier volume pricing unless they are very expensive like the Mj2119x parts.
I do suggest that you use the MJ2119x parts. We blew the original Toshiba o/p bjts a number of times, until I put in the higher powered Motorola bjts. When we were kids we blasted the heck out out of the 950 at parties.
Also glue the leads/sleeves where they enter the STV diodes, to secure them so they do not break on you. I do this to everyone I see.

 

[kevzep]

I had this SX1250 fail under a full load test, two original output transistors let go, damaged some emitter resistors along the way....
So I can agree with Rick, put some MJ21193/94 in there, once I had those installed, it passed its full load test....I have a decent arbitrary composite wave file for putting amps under stress. Works well, and will find anything weak!!

 

[CavScout]

531-PT10H-100 is 100 ohms. It is probably better than the originally spec'd part. if the Bourns parts fit properly go for it.

I always fill by Mouser order with >=$100 CDN (it is not hard to do) and get next day or following day free shipping to my door, it is fantastic service. Digi-key is the same. I am sure kevzep would love to have this service we are fortunate to have in Canada. A full re-cap, semi replacement will get you over 100 quite easy.
never hurts to have some spare components on hand.
From what I have read here you have issues for which you need to have some spare parts on hand to fix your issues. Ohm out all the resistors, diodes, bjts before you order parts
Do you need a list?
For the amp bjts, ksa992f, ksc3502, ksa1381, KSB596Y, KSD526Y and the o/p's if needed MJ211 93/94 or 95/96, TO-3 micas, paste. I always order min 10 of bjts/diodes/resistors/ecaps to get the next tier volume pricing unless they are very expensive like the Mj2119x parts.
I do suggest that you use the MJ2119x parts. We blew the original Toshiba o/p bjts a number of times, until I put in the higher powered Motorola bjts. When we were kids we blasted the heck out out of the 950 at parties.
Also glue the leads/sleeves where they enter the STV diodes, to secure them so they do not break on you. I do this to everyone I see.

I do need to make a list but being a novice I am concerned I will get the wrong stuff. Also not sure which parts to get.
Can you PM me an actual list with quantities based on your experience?

 

[1MEGΩ]

I do need to make a list but being a novice I am concerned I will get the wrong stuff. Also not sure which parts to get.
Can you PM me an actual list with quantities based on your experience?

Well, before you order anything, you still need to figure out why you are getting those readings across the Emitter and Collector of Q9 and across the Base and Emitter of Q11. If you aren't sure how to determine where the problem is, you have 2 identical circuits on the Audio Amp board. The left channel and the right channel. Compare the components around Q9 and Q11 to the components around Q10 and Q12 and try to figure out which components are causing those readings. Use your ohm meter for this. For starters, you can check D7 and D9 for shorts with your meter set to ohms. You can compare those diodes to D8 and D10 in the right channel. You do not need to lift the leads of the diodes to check if they are shorted.

 

[rcs16]

I agree with above.

 

[CavScout]

Well, before you order anything, you still need to figure out why you are getting those readings across the Emitter and Collector of Q9 and across the Base and Emitter of Q11. If you aren't sure how to determine where the problem is, you have 2 identical circuits on the Audio Amp board. The left channel and the right channel. Compare the components around Q9 and Q11 to the components around Q10 and Q12 and try to figure out which components are causing those readings. Use your ohm meter for this. For starters, you can check D7 and D9 for shorts with your meter set to ohms. You can compare those diodes to D8 and D10 in the right channel. You do not need to lift the leads of the diodes to check if they are shorted.

When you say I do not need to lift the leads of the diodes does that mean that I have to remove everything else from circuit to test ?

 

[petehall347]

compare to good channel if you find anything reading out of spec in bad channel . search and destroy ..

 

[1MEGΩ]

When you say I do not need to lift the leads of the diodes does that mean that I have to remove everything else from circuit to test ?

NO! Do not remove anything from the circuit. What I am saying to you is you do not have to remove the diodes to test them. Leave everything as is and simply test the diodes with your ohm meter set to ohms. Also, polarity does not matter when checking a component for a short. You just want to make sure the diodes do not read low resistance or 0 ohms.

 

[CavScout]

I finally received the new vr trim pots and installed them. Any idea what to do next ?

 

[CavScout]

NO! Do not remove anything from the circuit. What I am saying to you is you do not have to remove the diodes to test them. Leave everything as is and simply test the diodes with your ohm meter set to ohms. Also, polarity does not matter when checking a component for a short. You just want to make sure the diodes do not read low resistance or 0 ohms.

The readings were identical on both sides

 

[petehall347]

you need to set to min bias if bias pots ..if offsets set centred

 

[CavScout]

Not sure what you mean.
Vr1 and vr3 are bias ?
Vr2 and vr4 are DC offset?
Sorry, still learning

 

[CavScout]

Pics of the new trim pots

 

[petehall347]

3 and 4 appear to be bias ..the others offsets .
use dbt to save problems ..
wait for someone who can explain better than i ...

 

[1MEGΩ]

Not sure what you mean.
Vr1 and vr3 are bias ?
Vr2 and vr4 are DC offset?
Sorry, still learning

VR1 and VR2 are for DC offset and VR3 and VR4 are for bias. These new pots you just installed are 25 turn pots. I chose those because it will make it much easier for you to adjust the offset and bias. The first thing you need to do now is turn each pot adjustment counterclockwise 25 full turns. Now turn VR1 and VR2 twelve and a half turns clockwise to set them midway for DC offset. This will put you very close to 0 volts DC in each channel. Leave VR3 and VR4 alone for now. Disconnect all speakers and turn the volume control all the way down and choose AUX mode. Power up your 950 with a 60 watt light bulb in series with your power cord. Be sure you do this correctly. Now turn on the power switch and verify the bulb goes dim after a few seconds and STAYS dim. Let me know the results. I want to go through this with you one step at a time.

 

[CavScout]

Thanks for the detailed Instructions.
I did what you said but the reading on Vr1 stays at -49.75 v DC regardless which way I turn it.
I checked my connections from the voltmeter to the pins and they are good. Vr2 is right around 0 v DC.
Perhaps something else upstream has blown ?
When I first turned on the unit the bulb went very bright and then went dim.

 

[1MEGΩ]

Thanks for the detailed Instructions.
I did what you said but the reading on Vr1 stays at -49.75 v DC regardless which way I turn it.
I checked my connections from the voltmeter to the pins and they are good. Vr2 is right around 0 v DC.
Perhaps something else upstream has blown ?
When I first turned on the unit the bulb went very bright and then went dim.

Where exactly are you reading -49.75 volts DC? Are you reading voltage directly on the pots? If so, why? The DC offset voltages are to be taken between pin 9 or chassis ground and pin 10 for the left channel and between pin 24 or chassis ground and pin 25 for the right channel. Is the bulb staying bright at all times now?. I figured you would have problems in the left channel because of the problem with Q9 and Q11 which you haven't solved yet. Anyway, be more specific when giving voltage readings.