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SONY 5650 Vfet amp advise before I start

gummy said:
vint age,
have you taken your pills today.
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happy-smiley58.gif
 
gummy said:
Well I have tried to carry out ecowars instructions (using my DVM see pic) and here are the results.
Tested on 800KOhm range. 2SK60 transistor 1 = 1.9. 2 = 2.1 3 = 2.4 4 = 1.8 5 = 2. 6 = 1.9 7 = 2.0 8 = 0.9
Now the diode test, gate to source transistor 2SJ18 1 = 0.525 2 = 0.524 7 = 0.547 8 = 0.239 on reverse source to drain they are they same or within 0.001 these are the PNP ones.
Now for the others 3 = 0.565 4 = 0.564 5 = 0.564 6 = 0.562 on reverse gate to drain the readings are the same. on the last check on ecowars post they are all OL except No8.

So it seems No 8 is kaput, HELP I need a 2sj18 transistor HE-54 rank, I thought I had located some NOS transistors but on checking they were not Vfets, little diode has some replacements but are unable to supply any tech info on them, If anyone can Help it would be most welcome, if I am unable to get replacements it's a waste of time carrying out any restoration of this amp, as you have probably surmised I am a complete newbie to this hobby but I am trying to do my best, with your help I may triumph.
Thanks all.
Wal
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Wal,

You are so lucky, only one out of eight VFETs down, normally they prefer collective sudden death by the channel.... which BTW is already giving prelimanary indications that it might be the usual oxidation of the sockets, though I wouldn't dare to jump to too easy conclusions.

The issue here being to find a matching VFET. Matching by rank number is a general 'safe' approach, though in fact, matching of VFETs is rather done by pinchoff voltages. I don't recall Little Diode having 5x rankings at all, but you could shoot an email to them. Perhaps, and I stress perhaps, I may know somebody who has a single 2SJ18, but give me a month or more to get in touch with this person.

Another issue is that you should really well rebuild this amp before ever powering it on again; either by really well preparing and knowing what you are up to (little error margin, as errors can fry your VFETs easily), or find a person who is familiar with it.

Again, you are lucky !

ozzy
 
There have been many 5650 rebuild threads over the last years here, this is another usefull one where EW contributed a lot of good knowledge.
 
EchoWars said:
Yep...unless you have a dead VFET too. ;)
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oh well, I took the habit by now to purchase multiple half working 4650 units to get one 5650 working...

Seriously, I'm actually looking for an amp PCB + chimneys of a 5650 unit, if anybody has those ? Even if half the components are diep-fried I'll be happy. Otherwise I will have to start duplicating the boards myself one of these days.
 
Hi.
Thanks you all for your help, will a 2sj18 with rank No HA56 work as a replacement.
ecowars I am located in "The Land Of Song" Wales that is, you know that little country in the west of England, have you ever listened to a full Welsh choir, magic.
Well folks what's the next move in the refurbishment of this amp, I'm afraid I am going to try and do it myself as we have no one in this area capable of doing it. so help and advice will be welcome.
Thanks again.
Wal.
 
gummy said:
Hi.
Thanks you all for your help, will a 2sj18 with rank No HA56 work as a replacement.
ecowars I am located in "The Land Of Song" Wales that is, you know that little country in the west of England, have you ever listened to a full Welsh choir, magic.
Well folks what's the next move in the refurbishment of this amp, I'm afraid I am going to try and do it myself as we have no one in this area capable of doing it. so help and advice will be welcome.
Thanks again.
Wal.
Click to expand...

if your VFET are ranking 54, than you should not insert a single 56 in them. If you change ranking, then all VFETs of the channel concerned should be changed. The guy I know who may have one VFET in his drawer lives in the UK as well, let's hope it is the same ranking, I'll send you a PM. PS: if echowars may have something to offer, I would check it out.
 
Forgot to ask has anyone got a decent scan of the service manual, mine is a scan of a photocopy so not very clear.
Thanks.
Wal
 
gummy said:
have you ever listened to a full Welsh choir, magic.
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Is that what you were playing when the incident happened? :D

Concerning a manual, Sony SM are a real PITA to scan, schematics are printed over 3 pages wide fold-outs. Best option would be this one.


And reading a lot of threads on this forum.
 
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