sx-1250 power amp SMOKED help
- Thread starter arranb
- Start date
Compare them to the other working board. Post the second board's readings, it would be nice if the Q's were in some sort of order.. q1, q2 and so forth...
Most of these ... well... they stink...
Q4, Q5 and Q6 look ok.
without 0.6v the transistor is off, and all but the over current detector Q11 should be ON, on this board.
And any emitter to base voltage over five volts of the correct polarity means the transistor has been blown away.
The compare to a working board is to confirm you were hitting the right spots for the readings.
Most of these ... well... they stink...
Q4, Q5 and Q6 look ok.
without 0.6v the transistor is off, and all but the over current detector Q11 should be ON, on this board.
And any emitter to base voltage over five volts of the correct polarity means the transistor has been blown away.
The compare to a working board is to confirm you were hitting the right spots for the readings.
Got it, I did check the other board and yes I did see proper voltages. Q11 was the only one not working. I was going to ask about that later but no need now. I'm thinking a complete rebuild of this board. It is the one that shorted out when the stv3 diode grounded out. Should I just replace all transistors, diodes and caps? I replaced a bunch of parts on both boards and this one works But I cannot adjust the voltages correctly. Maybe I missed a crucial part that caused issues again. Funny thing is that it does put sound out.
and I'm quite a bit OCD...
In the past I would have just quoted the list and rearranged it to work with it (DID I check THAT reading??) and keep track of what I was doing. But in calling attention to it, I don't have to repeat that for every subsequent set of readings.
Multiply that by 5 to 20 or more threads a day and we're talking about some significant amounts of time here...
back OT:
Any parts replacements since the stv lead (Broke? grounded? etc???)
which transistors are original, which are replacements and what are the parts numbers of the replacements. What other parts were replaced by you. It helps when trying to "trace the lightning bolt"...
From the numbers in those readings there are are just a few working transistors on that board. That it passed sound is surprising. Lower voltages aren't as worrisome, pushing sound in might turn them on, albeit with a lot of distortion, but the ones with too much emitter to base voltage are worrisome...
I was hoping that there were more probe placement errors than blown transistors. That hope is diminishing.
Quite frankly, out of circuit 6 way diode transistor tests(see post #11) are warranted on everything (I expect q4,q4,q6 may test good) and a sound investment in time and effort.
In the past I would have just quoted the list and rearranged it to work with it (DID I check THAT reading??) and keep track of what I was doing. But in calling attention to it, I don't have to repeat that for every subsequent set of readings.
Multiply that by 5 to 20 or more threads a day and we're talking about some significant amounts of time here...
back OT:
Any parts replacements since the stv lead (Broke? grounded? etc???)
which transistors are original, which are replacements and what are the parts numbers of the replacements. What other parts were replaced by you. It helps when trying to "trace the lightning bolt"...
From the numbers in those readings there are are just a few working transistors on that board. That it passed sound is surprising. Lower voltages aren't as worrisome, pushing sound in might turn them on, albeit with a lot of distortion, but the ones with too much emitter to base voltage are worrisome...
I was hoping that there were more probe placement errors than blown transistors. That hope is diminishing.
Quite frankly, out of circuit 6 way diode transistor tests(see post #11) are warranted on everything (I expect q4,q4,q6 may test good) and a sound investment in time and effort.
Well, Well,Well.......After so much aggravation and testing I have finally fixed my Lovely SX-1250!!!!! Can anyone tell me if there is a mistake in the manual on R36 and R37? It says 4.7 1w on both. I replaced them with part number 660-spr1ct52a472j from mouser. I only replaced them on one of the boards and couldn't get 0.6v between the base and emitter of all transistors in fact I was getting 10.0v on q10! The only ones getting the correct voltage were Q4,Q5, and Q6. After almost destroying all the solder pads by removing and replacing them over and over I discovered the magic voltage number that was holding me up was 4.7. So, Tonight i decided to go over every part I replaced and match the values with my working board and when checking R36 and R37 I found the working boards values at 0.06 and the new resistor at 4.7 which is what made me think, Huh I wonder if that is whats giving me the voltage thats not needed on other parts of the board.So I installed the old resistors and VIOLA! So is the manual wrong or is there something else wrong with my receiver that likes the bad resistors and allowed me to adjust the voltages correctly? Oh and the DBT goes completely out.
Thank you all for helping me! I appreciate it very much. 25 bucks a year is well worth the investment to be a member here. I'm not done with repairs. This has made me more interested than I was before.
HAPPY NEW YEARS TO ME! MY SX-1250 IS WORKING!!!!!@@@!@#R@IYE*&@^E_(*{H@PXIO@HD*&G@OI"LDKN{(&@TC({*O@IJDOYH)*"IPJMFD
HAPPY NEW YEARS TO ME! MY SX-1250 IS WORKING!!!!!@@@!@#R@IYE*&@^E_(*{H@PXIO@HD*&G@OI"LDKN{(&@TC({*O@IJDOYH)*"IPJMFD
660-spr1ct52a472j is 4.7K or 4,700 ohms... looking back to see HOW you got THAT number!!
Ok, the BOM lists:
r36 metal film 4.7 1W RN1H 4R7K
urgghhh, it's from MY resistors list....
660-spr1ct52a472j
660-spr1ct52r4R7J
How he HECK did I do that???
BUT it gets better, the spr series is CARBON film...
we want metal film...
thus:
594-5073NW4R700J
and it's LESS expensive at $0.16 ea as opposed to $0.25 ea for carbon film...
Ok, the BOM lists:
r36 metal film 4.7 1W RN1H 4R7K
urgghhh, it's from MY resistors list....
660-spr1ct52a472j
660-spr1ct52r4R7J
How he HECK did I do that???
BUT it gets better, the spr series is CARBON film...
we want metal film...
thus:
594-5073NW4R700J
and it's LESS expensive at $0.16 ea as opposed to $0.25 ea for carbon film...
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I'm sure I got that from a post somewhere. Either way I am very happy right now. Listening to Led Zeppelin "No Quarter" Enjoying every bit!. Wish I had better speakers Than theses Klipshhe kg2's. But hey I'm very happy I have this receiver working! I'm sure some of you can understand the feeling I have right now! And a very large thank you to Mark The Fixer and everyone else who chimed in for all your help!
Look at it this way. Given the quantity and depth of things you research, compile, update, and post, by the percentages of error the "hiccups" are infinitesimally small in number. Your SPC is looking pretty damn good.
It's also good to see that you're human.
I'm backtracking all 660-spr1ct52a472j references through the forum right now...
hang on...
A search reveals the first PUBLIC appearance of that list is in zebulon1's 01-23-2014, 02:50 AM post which I am unclear if I provided the list to him privately, or if the spreadsheet list I have was generated off this post. (edit - according to the thread, I inhaled it into my spreadsheet... )
Me thinks we BOTH missed it, cuz I did kibbitz a lot in the thread after the list appeared, and - had I just redone the list, there it was ....
hang on...
A search reveals the first PUBLIC appearance of that list is in zebulon1's 01-23-2014, 02:50 AM post which I am unclear if I provided the list to him privately, or if the spreadsheet list I have was generated off this post. (edit - according to the thread, I inhaled it into my spreadsheet... )
Me thinks we BOTH missed it, cuz I did kibbitz a lot in the thread after the list appeared, and - had I just redone the list, there it was ....
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I will say I have learned a TON from this. Ironically a customer of mine sold me a hitachi oscilloscope v-212 today. I told him I was learning how to repair electrical stuff and thats what he brought in the shop today. A new tool for me to learn from. By the way I like both of your quotes. I may have to think of one for myself. As far as the list It's my fault for not checking on all the part numbers myself. It's a lack of knowledge I'm aquiring and will be more careful in the future. (or at least try)
For now I am going to take a break on this project. The tunes are flowing and the voltages are correct! I will say here's a little advice from me. When going through the diagnostics process here on AK as a rookie, Listen to all the advice from the experts and follow the instructions given to you exactly as they say. If I would have done that I this forum would have been done a long time ago. MTF asked me to post an entire list of all the parts I had replaced and I didn't follow thru. Had I done that we would have found the incorrect resistor part number and corrected it right away and I wouldn't have chased my tail trying to figure things out. I will say I have spent a lot of time learning about electronics and feel more comfortable moving on to my next project.
I hope all of you had a merry christmas and have a Happy new Year! I will be at the hospital welcoming our new son into this world!
I hope all of you had a merry christmas and have a Happy new Year! I will be at the hospital welcoming our new son into this world!
I am happy you got the 1250 up and running. What a great feeling it is to have something so important to us fixed (Certainly a relative statement). It is the combination of enjoyment and frustration at it's near peak. I find it, a test against ones self. :scratch2:
I hope I didn't hinder your thread in a bad way. This forum is really dedicated to precise information and trusting advice. :yes:
I am wondering if you had picked out the next project? :thmbsp:
I hope I didn't hinder your thread in a bad way. This forum is really dedicated to precise information and trusting advice. :yes:
I am wondering if you had picked out the next project? :thmbsp: