This Yamaha had a think piece of plastic and some kind of thermal paste between a couple of the diodes and a big heat sink.
Do you just use CPU thermal paste?
They are mounted vertically, so if it was something runny it might run down the side.
Photo?
guess I need to shrink the photo sizes
Try this again
wow thats huge
sorry about that
Testing attachment size
Note to self 780x585 is better
Should I stick to one post and change the subject to just Yamaha G100-112?
Quote from: dlbraly on July 18, 2018, 09:30:28 PM
Should I stick to one post and change the subject to just Yamaha G100-112?
Yes that would be easier to follow. :tu:
Adding;
Those are not diodes,, them big suckers is Power transistors.
TR311 &TR312 on the schematic.
The white goo is thermal paste, Yes same for CPU's,, all the same stuff.
The plastic pad is a mica isolating washer which isolates the case (which is also the collector) from the heat sink.
The newer pads maybe synthetic types which are are not so brittle but mica works just as well.
The thermal paste is to help transfer the heat from the collector across to the heat sink,,, and Always use it!! :trouble
When you reinstall those power transistors with washer and paste check with meter to make damn sure that the both collectors (The transistor case) is actually isolated from the heat sink otherwise it will end in tears at switch on. :o
Phil.
Quote from: phatt on July 18, 2018, 10:53:06 PM
Quote from: dlbraly on July 18, 2018, 09:30:28 PM
Should I stick to one post and change the subject to just Yamaha G100-112?
Yes that would be easier to follow. :tu:
Adding;
Those are not diodes,, them big suckers is Power transistors.
TR311 &TR312 on the schematic.
The white goo is thermal paste, Yes same for CPU's,, all the same stuff.
The plastic pad is a mica isolating washer which isolates the case (which is also the collector) from the heat sink.
The newer pads maybe synthetic types which are are not so brittle but mica works just as well.
The thermal paste is to help transfer the heat from the collector across to the heat sink,,, and Always use it!! :trouble
When you reinstall those power transistors with washer and paste check with meter to make damn sure that the both collectors (The transistor case) is actually isolated from the heat sink otherwise it will end in tears at switch on. :o
Phil.
Thank You - Will do
OK, so changed the subject so that everything will be one place.
Some Pictures
Those first ones are the dirty PA board
Then The DC board before and after
The MA board before and after I put everything back on
Um, blanking a board like that is not a good idea. You run the risk of damaging parts in the process and making reassembly mistakes, soldering errors can occur as well.
Quote from: Enzo on July 19, 2018, 02:17:07 AM
Um, blanking a board like that is not a good idea. You run the risk of damaging parts in the process and making reassembly mistakes, soldering errors can occur as well.
LOL now you tell me.
Yeah, I'm learning a lot from my mistakes. I should have asked questions before starting was one HUGE mistake. Could have been a quick fix.
Yes, tiss a bit like pulling out the engine because you found a loose wheel nut. :duh
Remember that just about any part on the pcb is replaceable,, except the pcb itself. :o
On old pcb's it easy to de-laminate the pads which can be a nightmare to fix.
So be very careful not to damage the traces and pads. :-X
Phil.
Not only that, but it is a mistake to assume the problems are always caused by bad parts. You could have a crack in a copper trace. You could replace every part on the board, but the cracked trace would remain.
Yeah, I've been known to jump in with both feet. :o
Picked up some thermal Paste, got the amp back together.
I bought 2 NTE458 transistors to replace the bad transistor 2SK30A (replaced the pair of them).
I did not not try the amp without the transistors like Enzo suggested. I was there getting the paste...
The amp is now loud like it should be.
BUT,
There is a very loud popping noise. Ive twisted all the pots and it doesn't seem to make a difference in the popping.
Turn the amp on with or without guitar after about 15 or 20 seconds it starts a loud sporadic popping. Turn the amp off, then back on another 15 seconds or so it starts again.
I did notice that sometimes when you turn the amp off, you can hear some static sound from the speaker for a few seconds. Im not sure if that is normal for this amp.
Would the 2 transistors I replaced (TR206 and TR207) cause that type of fault?
I have NOT done the adjustments yet that the service manual says to do. Figured I'd post here first. Then go back in and see if I can do that.
OK, so TR206 and TR207 can cause that popping!
I removed them, and I cleaned the pots.
Enzo rocks! I should have just listened to him in the first place. Thanks.
I will mess around with it some more, and to make sure nothing else is wrong with it. I also need to do some very minor cosmetic stuff to it.
There is a tiny tear that I don't want to get any bigger.
and someone replaced a pot, but put one in that the shaft was too big, and just cut it off to fit. but the knob doesn't stay one. I'm going to try and cut a slit it in it since it now longer has one.
I think my Dad will be happy with it.
That Yamaha Amp really sounds good. :dbtu:
My Dad asked me if I wanted to use it a little longer. I told him he better take it because all I'm dong is playing on it. I'm not getting my other stuff done.
Yamaha really made a sturdy amp. the wood in the cab was real thick and heavy!
Im curious if the Series II and III are as heavy duty.
Anyone have any idea?
What are your thoughts on Yamaha Amps? Good, Bad, just OK?
I blogged on it. Nothing more that is not posted here.
My Blog (https://bfixitstop.blogspot.com/2018/07/yamaha-g100-112-repair.html)
All the old Yamaha stuff was quality gear.