Tomorrow I should have the board re-worked. More then.
James
Yamaha M-70 Thread
- Thread starter Bratwurst7s
- Start date
Tomorrow I should have the board re-worked. More then.
James
That's looking fantastic james.
Thanks boza! I just hope that it ends up sounding the same way.
Cheers,
James
Could that have been the whole problem with it?
I'm really struggling to understand this thing at all, I'm really just not that good at reading and understanding schematics yet. My Meister friend took a short look at the X-power control circuit, understood it immediately, and tried to explain to me how "Elegant" and effective it is. It just makes me dizzy.
But, if I'm understanding things correctly C702 sits in parallel to zener D703 and feeds voltage to the base of TR701, which is responsible for feeding 12v to the lamps and protection and ?. So if C702 has no connection then no +12v? Between this and the bad connection on the emitter of TR602 I think that they would play hell on the amp and I'm hoping that I've found the smoking guns that would cause someone to forceably rape those traces on the main cap board.
But I'm not sure if I have all of that anything close to correct.
Cheers,
James
edit: After talking with my tech friends my above speculation/guess about C702 seems to be incorrect. Their conclusion is that the cap is just doing a small amount of local filtering and loosing it's connection wouldn't have a major effect on the amp's operation.
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Mr. Yamaha
Not so much Yamaha lately...
Ouch, you gotta love that corrosive glue they used
Yes, "That Glue". The cause of much heartache in these forums.
Still, considering the way it looked there were no components that were actually out of spec on the board, aside from the partly missing cap leg. I guess that's out of spec.
But the caps measured reasonably good considering their age.
C701: 4700µF/16v = 4287µF/0.07ohms. Replaced with UCC KYB 4700µF/35v, measured 5325µF/0.03ohms.
C702: 10µF/16v = 10.68µF/2.2ohms. Replaced with Wima MKS2 10µF/50v.
C703: 1µF/50v = 1.04µF/4.0ohms. Replaced with Wima MKS2 1µF/63v.
C704: 10µF/50v = 10.59µF/2.1ohms. Replaced with Wima MKS2 10µF/50v.
C705: 1000µF/100v = 944.3µF/0.04ohms, Replaced with UCC KYB 1000µF/100v, measured 1020µF/0.01ohms.
C706: 1000µF/100v = 928.0µF/0.05ohms, Replaced with UCC KYB 1000µF/100v, measured 1024µF/0.02ohms.
The resistors all checked good and reasonably close to spec. They were all replaced with Vishay metal film except for the 8.2ohm MOX, replaced of course with another 2w MOX. I don't know what's with me concerning forgetting resistors when I order parts. Seems that I forgot the 33K that I needed. I got frustrated and sorted through my 15k and 18.2k until I found a 14.8k and 18.22k and wired them in series for R706. Not an elegant solution but it did at least work.
The S2VB20 bridge rectifier was replaced with a BR62, specs are more than good enough.
The WZ-120 zener was replaced with a BZX55B12-TAP 12v.
The 1S1855 diode was replaced with a MUR160RLG.
The W06C diodes were replaced with UF4005's.
The S2VC10 was not replaced at this time. The STTH1002CT that I ordered went back-order. This is also the only part that wasn't removed. After seeing that al of the other parts checked good I decided to save the heating it would take to remove, check, and re-install and just re-flowed it's connections. This is the only real risk that I see that I took on this board but I don't feel bad about it.
TR701 2SC2235O was replaced with a KSC2316YTA.
TR702 2SC1983 was replaced with a TIP122-BP.
The rest of the solder connections were de-soldered, cleaned and re-soldered.
Cheers,
James
Still, considering the way it looked there were no components that were actually out of spec on the board, aside from the partly missing cap leg. I guess that's out of spec.
But the caps measured reasonably good considering their age.
C701: 4700µF/16v = 4287µF/0.07ohms. Replaced with UCC KYB 4700µF/35v, measured 5325µF/0.03ohms.
C702: 10µF/16v = 10.68µF/2.2ohms. Replaced with Wima MKS2 10µF/50v.
C703: 1µF/50v = 1.04µF/4.0ohms. Replaced with Wima MKS2 1µF/63v.
C704: 10µF/50v = 10.59µF/2.1ohms. Replaced with Wima MKS2 10µF/50v.
C705: 1000µF/100v = 944.3µF/0.04ohms, Replaced with UCC KYB 1000µF/100v, measured 1020µF/0.01ohms.
C706: 1000µF/100v = 928.0µF/0.05ohms, Replaced with UCC KYB 1000µF/100v, measured 1024µF/0.02ohms.
The resistors all checked good and reasonably close to spec. They were all replaced with Vishay metal film except for the 8.2ohm MOX, replaced of course with another 2w MOX. I don't know what's with me concerning forgetting resistors when I order parts. Seems that I forgot the 33K that I needed. I got frustrated and sorted through my 15k and 18.2k until I found a 14.8k and 18.22k and wired them in series for R706. Not an elegant solution but it did at least work.
The S2VB20 bridge rectifier was replaced with a BR62, specs are more than good enough.
The WZ-120 zener was replaced with a BZX55B12-TAP 12v.
The 1S1855 diode was replaced with a MUR160RLG.
The W06C diodes were replaced with UF4005's.
The S2VC10 was not replaced at this time. The STTH1002CT that I ordered went back-order. This is also the only part that wasn't removed. After seeing that al of the other parts checked good I decided to save the heating it would take to remove, check, and re-install and just re-flowed it's connections. This is the only real risk that I see that I took on this board but I don't feel bad about it.
TR701 2SC2235O was replaced with a KSC2316YTA.
TR702 2SC1983 was replaced with a TIP122-BP.
The rest of the solder connections were de-soldered, cleaned and re-soldered.
Cheers,
James
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After finishing the +12v board I went back and mounted the 2nd bridge rectifier on the cap board along with the heat sink/mounting bracket.
Tomorrow I'll try to get these boards re-installed in the amp.
Oh. After sorting through my photos I see that I didn't take a single one of the trace side of the +12v pcb. But when I looked it over I didn't see a single solder connection that looked like someone had re-soldered anything here.
Cheers,
James
One note. When I was looking for replacements for the 4700µF/16v and 1000µF/100v I settled on the UCC KYB's because they had the highest ripple current rating of everything that I looked at, along with a pretty low ESR.
Cheers,
James
Cheers,
James
Doing the same thing here. Right now.
You probably have it much colder than here. It's only -5°c here right now. For Iowa in the winter that's probably like comfy sauna temps.
Cheers,
James
Its right around 0° C here.At least right now.
It's staying around -5° here today but at least we have blue sky, not so depressing as all of those grey clouds that we've been having for most of the winter.
I think that I'm going to have to take advantage of it and go for a nice walk with Wife.
Cheers,
James
But before going for that walk here are some progress photos.
Re-assembling the front of the amp went very straightforward and easy. Since there isn't really much holding the caps board in place it seems that the foam that acted as a clamp on the big caps was fairly important to keep it stable. The caps have 10mm less dia than the old ones so I added a piece of 6mm closed cell foam front and back to keep them cushy.
Cheers,
James
Re-assembling the front of the amp went very straightforward and easy. Since there isn't really much holding the caps board in place it seems that the foam that acted as a clamp on the big caps was fairly important to keep it stable. The caps have 10mm less dia than the old ones so I added a piece of 6mm closed cell foam front and back to keep them cushy.
Cheers,
James
It was actually easier to get the +12v card back in place than removing it. And the little transfer card on the lower left got it's connections re-soldered also, along with the 4 connections on the bottom right of the +12v card.
Next up is re-flowing all of the connections on the speaker switch and volume cards before re-installing all of that. I'm seriously considering non-permanantly bypassing all of that and just having speaker-A active with no attenuation or switching. It would shorten the signal path by almost a meter and take the switches and pots out of the signal path.
I've only taken a quick look at the schematic but it looks like the input could be run directly to the pre-drive card and the speaker connection jumpered at the socked on the main board.
Cheers,
James
Next up is re-flowing all of the connections on the speaker switch and volume cards before re-installing all of that. I'm seriously considering non-permanantly bypassing all of that and just having speaker-A active with no attenuation or switching. It would shorten the signal path by almost a meter and take the switches and pots out of the signal path.
I've only taken a quick look at the schematic but it looks like the input could be run directly to the pre-drive card and the speaker connection jumpered at the socked on the main board.
Cheers,
James
I only have a small progress report for now.
The small speaker switch and adj pot boards were re-flowed and cleaned and the board re-installed. At this point I have not deoxed the pots or switches.
I spent some time going over the work that I've already done, doing a QC check. And after looking carefully at the replacement that I made for the S1WB20 bridge D608 realized that it is wrong. I got stupid and built it with the anodes and cathodes of my SBYV27 diodes reversed. I can't explain that mistake but it is/was definitely wrong. Today I tested the original part and it checked good so I removed my incorrectly built part and re-installed the original.
Cheers,
James
The small speaker switch and adj pot boards were re-flowed and cleaned and the board re-installed. At this point I have not deoxed the pots or switches.
I spent some time going over the work that I've already done, doing a QC check. And after looking carefully at the replacement that I made for the S1WB20 bridge D608 realized that it is wrong. I got stupid and built it with the anodes and cathodes of my SBYV27 diodes reversed. I can't explain that mistake but it is/was definitely wrong. Today I tested the original part and it checked good so I removed my incorrectly built part and re-installed the original.
Cheers,
James
I've gone completely through the protection section now except for some of the resistors that I can't get at without pulling the board. Every part that I pulled checked good except for one oddity.
When I check the parts with my little 328 tester I usually run it 4 to 5 times because there are always small variations between each test with that thing. Usually very small variations (like ca 1% or less) and I take an average. But D135 gave large differences with each test. It checked good with each test, and also checked good using diode test with my multimeter, but each test run showed large differences, like ca 20%. All of the other diodes that I pulled had very stable test results. D135 is connected to the speaker-A relay.
C151 was replaced with a Panasonic FM 33µF/35v, the old cap checked at 30.96µF/0.09ohms/0.7%vLoss. Of course it was not as old as the others, being the Nichicon FG that someone installed. The new one measured 35.5µF/0.026 ohms/0.9% vLoss.
C152 was replaced with a Panasonic FM 100µF/25v, the old cap measured 99.9µF/0.66ohms/2.3% vLoss, the new one 102.0µF/0.1ohms/0.8%.
C153 was replaced with a Wima MKS2 0.022MF/63v.
D129, 130, 131, 133, 135 and 136 were replaced with 1N4148's.
D132 and 134 were replaced with TZX6v2D-TR's.
Note that the schematic shows R276 (10k ohms) installed in series before the anode of D130. On the board it is actually installed after the cathode.
TR171 was replaced with a KSA1220AYS, the old TR checked at hFe 182/vF 625mV, the new one 185/621mV.
TR172 checked hFE 99/vF 668. I kept it because the recommended KSA1013YTA specs seemed to be considerably different than the 2SA777.
TR173, 175 and 176 were replaced with matched KSC1815's. The old ones checked at hFe 167, 187 and 152, the new ones at 177.
TR174 was replaced with a KSA1015GRTA. The old TR checked 160/660 and the new one 279/665.
Interestingly the old relays are actually DPDT with the NC contact leads snipped off just like the new ones. They measured 156 and 153 ohms across the coils, with 193 and 189mH. The new ones measured 148 & 149 ohms, 207 and 201mh. I've yet to find any reference as to the purpose of the magnets that Yamaha placed on the relays next to the contacts on each side. So until/unless I read something different I re-installed them. If it becomes necessary to remove them they are easy to get at.
I forgot to check the front panel light bulbs when I had the +12v PS board removed. So I took a 9v battery and used it as a bulb checker. 4 of the 5 bulbs lit. The bad one is the protection lamp. So I'll have to use some mini-grabbers and hook a meter to the lamp posts when I first turn on the amp to get a protection indication until I get some replacement lamps.
I think that I'm ready to turn the amp on for the first time tomorrow after soldering the 470 ohm resistors in place of the output TR's. I hope that I'm guessing correctly that the driver TRs need to be plugged in when I start it.
Looking at my photos I see that there is still a little bit of green gunk in one of the lead holes of C151. I'll have to pull it and do a better job of cleaning the hole.
Cheers,
James
edit: corrected info about R276 position.
When I check the parts with my little 328 tester I usually run it 4 to 5 times because there are always small variations between each test with that thing. Usually very small variations (like ca 1% or less) and I take an average. But D135 gave large differences with each test. It checked good with each test, and also checked good using diode test with my multimeter, but each test run showed large differences, like ca 20%. All of the other diodes that I pulled had very stable test results. D135 is connected to the speaker-A relay.
C151 was replaced with a Panasonic FM 33µF/35v, the old cap checked at 30.96µF/0.09ohms/0.7%vLoss. Of course it was not as old as the others, being the Nichicon FG that someone installed. The new one measured 35.5µF/0.026 ohms/0.9% vLoss.
C152 was replaced with a Panasonic FM 100µF/25v, the old cap measured 99.9µF/0.66ohms/2.3% vLoss, the new one 102.0µF/0.1ohms/0.8%.
C153 was replaced with a Wima MKS2 0.022MF/63v.
D129, 130, 131, 133, 135 and 136 were replaced with 1N4148's.
D132 and 134 were replaced with TZX6v2D-TR's.
Note that the schematic shows R276 (10k ohms) installed in series before the anode of D130. On the board it is actually installed after the cathode.
TR171 was replaced with a KSA1220AYS, the old TR checked at hFe 182/vF 625mV, the new one 185/621mV.
TR172 checked hFE 99/vF 668. I kept it because the recommended KSA1013YTA specs seemed to be considerably different than the 2SA777.
TR173, 175 and 176 were replaced with matched KSC1815's. The old ones checked at hFe 167, 187 and 152, the new ones at 177.
TR174 was replaced with a KSA1015GRTA. The old TR checked 160/660 and the new one 279/665.
Interestingly the old relays are actually DPDT with the NC contact leads snipped off just like the new ones. They measured 156 and 153 ohms across the coils, with 193 and 189mH. The new ones measured 148 & 149 ohms, 207 and 201mh. I've yet to find any reference as to the purpose of the magnets that Yamaha placed on the relays next to the contacts on each side. So until/unless I read something different I re-installed them. If it becomes necessary to remove them they are easy to get at.
I forgot to check the front panel light bulbs when I had the +12v PS board removed. So I took a 9v battery and used it as a bulb checker. 4 of the 5 bulbs lit. The bad one is the protection lamp. So I'll have to use some mini-grabbers and hook a meter to the lamp posts when I first turn on the amp to get a protection indication until I get some replacement lamps.
I think that I'm ready to turn the amp on for the first time tomorrow after soldering the 470 ohm resistors in place of the output TR's. I hope that I'm guessing correctly that the driver TRs need to be plugged in when I start it.
Looking at my photos I see that there is still a little bit of green gunk in one of the lead holes of C151. I'll have to pull it and do a better job of cleaning the hole.
Cheers,
James
edit: corrected info about R276 position.
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I can't remember any audio project that I've done where I've made so many parts ordering mistakes as this one, especially concerning resistors.
So I opened my bag of 470 ohm resistors and I ordered... 10? Because I need 16? Well isn't that special.
Because I really don't want to go further without first testing the amp without OT's installed I'm going to have to wait until I can make another parts order next week. I have some other projects that need to be worked on in the waiting time.
Cheers,
James
So I opened my bag of 470 ohm resistors and I ordered... 10? Because I need 16? Well isn't that special.
Because I really don't want to go further without first testing the amp without OT's installed I'm going to have to wait until I can make another parts order next week. I have some other projects that need to be worked on in the waiting time.
Cheers,
James
While being able to borrow a 2nd multimeter is always nice, as the song says "God bless the child that has it's own". So yesterday I saw a Fluke 77 (1st gen) on ebay for €70 and took a chance and bought it.
I'm putting together a list of things to order from Mouser and should be placing an order tomorrow or Wed. That also lets me also order a couple of 0.01µF/250v safety caps for the power switch that I missed earlier.
Cheers,
James
I'm putting together a list of things to order from Mouser and should be placing an order tomorrow or Wed. That also lets me also order a couple of 0.01µF/250v safety caps for the power switch that I missed earlier.
Cheers,
James
