What (precisely) does 'ohmed' mean?
Are you saying that there was absolutely no leakage when reverse biasing junctions or from collector to emitter?
Are you saying that there was absolutely no leakage when reverse biasing junctions or from collector to emitter?
I did a simple short test but not for leaking, I'm just googling it now to figure out how to do a proper test.
Search the basic repair page for 'If you need help checking transistors'. Fill in the form and post the screen caps of the filled in form for both transistors.
It's odd that they are so different on diode check but I don't' see any leakage.
What is the DC voltage on pins 9 and 10 (black probe on pin 7 of the 494)?
What is the DC voltage on pins 9 and 10 (black probe on pin 7 of the 494)?
with no remote lead.
7-9 = 12.58v
7-10 = 13.00v
with remote connected.
7-9 = 12.97v
7-10 = 13.57v
with no remote connected although with connected there isn't much difference..
TL594
1) 11.84v
2) 11.89v
3) 12.00v
4) 11.42v
5) 11.79v
6) 13.24v
7) 0.8mv
8) 13.75v
9) 13.52v
10) 13.68v
11) 13.75v
12)12.98v
13) 13.00v
14) 13.00v
15) 13.01v
16) 12.65v
TL594
1) 11.84v
2) 11.89v
3) 12.00v
4) 11.42v
5) 11.79v
6) 13.24v
7) 0.8mv
8) 13.75v
9) 13.52v
10) 13.68v
11) 13.75v
12)12.98v
13) 13.00v
14) 13.00v
15) 13.01v
16) 12.65v
so I managed to find a TL494cn in a parts amp so carefully removed that to fit in this amp along with Q7/8 and i think everything is OK. pulls 1 amp with remote hooked up and virtually nothing with just power/ground.
I'm just assembling this amp with both boards together now but having a little difficulty! the strips of silicone insulater keep shifting around whilst sliding the boards in, any tips on this and can I use kapton sheet instead of the silicone strips? kapton tends stay put a bit better!
The manufacturers recommend replacing the silicone pads. In my opinion, if you use heatsink compound on both sides, they are generally OK to reuse. If you apply heatsink compound between the pad and the sink, they should remain in place. Lift the board as high as possible when sliding it into the heatsink (let the transistors ride against the top side of the slot as you slide the board in).
Kapton MT would be OK. Don't use the kapton sheet that they're selling as a base for 3D printers. It's different (not as thermally conductive).
Kapton MT would be OK. Don't use the kapton sheet that they're selling as a base for 3D printers. It's different (not as thermally conductive).
ok I'll keep trying with the sil pad strips, the main problem is the amp is 80cm long and in 2 halfs so the 1st half goes in nicely then it all goes wrong! I'll get an assistant to help as ideally you need 4 hands!!
Hi marko and Perry, I did follow this thread with much interest, anyway as I'm not constant in visiting the forum so I didn't post my suggestion -or better my opinion- when you were working at 1rst half... i just wanted to say to first mount back pots on board as these amps are somewhat "touchy" like babies... and also re-solder as many "mean" parts is the wisest work that by itself could sometimes give the good result you're looking for! (especially for old pieces).
I understand this is not quite a professional, technical approach to repairs, anyway it works more times than expected... in my experience.
As re. to some difficulty in insertion of pcb in the heat sink, I have done several times for 480uhc and yes, it requires some attention but I guess we are talking of same amps, and they sure are 2pcs Pa2300 stucked together in the 94 cm chassis, it should have both end panels removed, 1rst lets say the one with RCA connectors (and small preamp board) and the 2nd on the other side with power cables and speaker connectors... in the center of the amp shoud be a metal "wall panel" where pre-signal cable is leaned on, and speaker + power cables are connected to terminals where they go accross to the other end. So, amps boards get in the heat sinks one in one side and second in the opposite side... you shouldn't find so much difficult following the Perry's suggestion to hold board up while inserting as transistors scratch on upper side of groove....after that you only have to put carefully back the clamps on them... there is just the exact room for them to go through inside the upper heat sink groove.... and yeah, hear that "old style" incredible but realistic headroom and dynamics those instruments are capable to reproduce.
I understand this is not quite a professional, technical approach to repairs, anyway it works more times than expected... in my experience.
As re. to some difficulty in insertion of pcb in the heat sink, I have done several times for 480uhc and yes, it requires some attention but I guess we are talking of same amps, and they sure are 2pcs Pa2300 stucked together in the 94 cm chassis, it should have both end panels removed, 1rst lets say the one with RCA connectors (and small preamp board) and the 2nd on the other side with power cables and speaker connectors... in the center of the amp shoud be a metal "wall panel" where pre-signal cable is leaned on, and speaker + power cables are connected to terminals where they go accross to the other end. So, amps boards get in the heat sinks one in one side and second in the opposite side... you shouldn't find so much difficult following the Perry's suggestion to hold board up while inserting as transistors scratch on upper side of groove....after that you only have to put carefully back the clamps on them... there is just the exact room for them to go through inside the upper heat sink groove.... and yeah, hear that "old style" incredible but realistic headroom and dynamics those instruments are capable to reproduce.
thanks manlog!
she is all put back together and I had some fun with her on the bench! my poor Tannoy speakers got a good work out!!
she is all put back together and I had some fun with her on the bench! my poor Tannoy speakers got a good work out!!
Happy if have been of some help to you, and if you're using Tannoy speaker (Edinburgh perhaps?) in your bench test...woah I guess you'll be all time anxious to get the final audition test of repaired machines... just for chronicle, only a couple days ago I was mentioning to a new friend, who was telling me of a new speaker release by DD for an 8" coaxial, that Tannoy was first manufacturer -at my knowledge- who made a 15" coaxial with internal driver having an incredible efficiency along with a top rate quality so much that BBC studios in England adopted immediately those speakers in their recording studios.... (this new I heard in early seventies by a musician here in Rome...) wow, so much time passed away!!
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