SX-950 Relay Bypassed and Burnt Resistors
- Thread starter Pageplayer
- Start date
Pageplayer
Active Member
Awesome!
Thanks Watthour.
I think these were in my last Mouser order. But my BOM notes didn't say where they were used.
I'll check after work.
Thanks Watthour.
I think these were in my last Mouser order. But my BOM notes didn't say where they were used.
I'll check after work.
Pageplayer
Active Member
Here's where I'm at so far..
Amp board Recapped and many resistors changed out..
Moving on to power supply and protection board
Amp board Recapped and many resistors changed out..
Moving on to power supply and protection board
Pageplayer
Active Member
Power Supply finished up today. All new caps and transistors
I have my replacement relay ready to drop in.
I have my replacement relay ready to drop in.
Pageplayer
Active Member
Yes...
I fact, I just soldered up the new relay, and without any Output transistors installed I decided to give it a short test!
The bulb goes dim pretty quickly and the relay clicks after 4-5 seconds..
I think that will be enough for today tho. Tomorrow I'll poke around and take some voltages..
I fact, I just soldered up the new relay, and without any Output transistors installed I decided to give it a short test!
The bulb goes dim pretty quickly and the relay clicks after 4-5 seconds..
I think that will be enough for today tho. Tomorrow I'll poke around and take some voltages..
petehall347
the brandy coffee man
looking good .
Pageplayer
Active Member
Oh!
Forget to mention, this came in the mail over the weekend..
Forget to mention, this came in the mail over the weekend..
kevzep
Its all about the Music
You have to be kidding!!! Me and my friends live our lives to this saying!! I need to get one of these Shirts!! Good old Buck!!
Pageplayer
Active Member
You know where I found it right?
I was so geeked when it came up in my search result.
Pageplayer
Active Member
welp.. Bad news.
As mentioned, I planned on taking voltages off the power supply tonight.
I printed out the diagram and grabbed a pencil and powered her on.
About 2 minutes in, I was about to take reading on pin 3 when I heard what I thought might be the relay click. About 8 seconds later, the dim bulb tester went bright I seen a puff of smoke come from Q4 as I simultaneously hit the power switch to off.
(No output transistors are connected to the power amp yet)
Q4 was indeed very hot to the touch immediately after the incident.
Looks like I'm starting over on the power supply again.
Would appreciate any feedback you all could provide.
As mentioned, I planned on taking voltages off the power supply tonight.
I printed out the diagram and grabbed a pencil and powered her on.
About 2 minutes in, I was about to take reading on pin 3 when I heard what I thought might be the relay click. About 8 seconds later, the dim bulb tester went bright I seen a puff of smoke come from Q4 as I simultaneously hit the power switch to off.
(No output transistors are connected to the power amp yet)
Q4 was indeed very hot to the touch immediately after the incident.
Looks like I'm starting over on the power supply again.
Would appreciate any feedback you all could provide.
petehall347
the brandy coffee man
did you change zd12 ? did you confirm transistor pin outs ?
Pageplayer
Active Member
On the Power Supply, The KSA1013YBU I placed in Q4 had correct pin out. (see image above)
I pulled the Zeners ZD1 & ZD2 and checked them with multimeter Diode setting during the rebuild. They checked good, but now ZD1 is passing voltage in both directions. ( I don't see a zd12 on diagram)
I'm continuing to pull and retest everything.
I pulled the Zeners ZD1 & ZD2 and checked them with multimeter Diode setting during the rebuild. They checked good, but now ZD1 is passing voltage in both directions. ( I don't see a zd12 on diagram)
I'm continuing to pull and retest everything.
petehall347
the brandy coffee man
it is marked zd12 on this schem . connects to q4 emitter
Pageplayer
Active Member
Correction: It was ZD2 that is bad.. In my schematic I'm seeing this...
kevzep
Its all about the Music
Yeah, a bit hard to test Zener's they are not like a normal diode. Just replace 'em, not a lot of extra cost and they do go flaky with old age......
kevzep
Its all about the Music
Yeah man, I just ordered two!! So happy I was reading through your post to see how you were going...
You know where I found it right?
I was so geeked when it came up in my search result.
Pageplayer
Active Member
I'm ready to try this again.. But thought I should check in with you guys first.
I have completely gone thru the Power Supply and Protection Board again, (since post #31)
Replaced the Zeners, and traced all wires from those boards just to make sure whom ever bypassed the relay didn't re-wire or bypass anything else.
No Output Transistors in Power Amp yet.
The smallest bulb I have for DBT is 60W...
I have powered it up for about 30 seconds to this point.. Bulb goes bright like normal then dims to a faint glow after a few seconds.
Relay is not clicking on. So I shut it down. Transistors are not getting hot at this point.
How should I proceed?
I have completely gone thru the Power Supply and Protection Board again, (since post #31)
Replaced the Zeners, and traced all wires from those boards just to make sure whom ever bypassed the relay didn't re-wire or bypass anything else.
No Output Transistors in Power Amp yet.
The smallest bulb I have for DBT is 60W...
I have powered it up for about 30 seconds to this point.. Bulb goes bright like normal then dims to a faint glow after a few seconds.
Relay is not clicking on. So I shut it down. Transistors are not getting hot at this point.
How should I proceed?
petehall347
the brandy coffee man
check dc offsets ..pin 10 and pin 25 .....amp board .
Pageplayer
Active Member
I can get dc voltage down to 0.100V
