Technics amp SU-CH9 no power ..possible repair?????

[rabbit@]

I will post a pic tomorrow .

It's quite weighty actually. If it was lightweight I would just tell my mate to bin it . Need to nip over there and retrieve the tuner. might be a few days though.

Sorry about this . appreciate your input .

You really do need a schematic to do/understand anything without a ton of experience and training. Can you take a picture with the case off? I was a Panasonic/Technics authorized for tech for 25 years. When I see a newer unit like this with a big fan I immediately suspect it has a PMPS. If it doesn't have a big PT with multiple secondaries and weighs nothing, it probably is. Maybe not, but usually. IMHE... Most power amp units will work stand alone. (But that does mean this one does.) Especially if it has a power switch. And you my be right about protection. If your friend shorted some speaker wires and fried an output device, it may not power up. BUT it would try to quickly before it detected the over current condition.

[rabbit@]

scuse my ignorance . what is a PMPS ?

You really do need a schematic to do/understand anything without a ton of experience and training. Can you take a picture with the case off? I was a Panasonic/Technics authorized for tech for 25 years. When I see a newer unit like this with a big fan I immediately suspect it has a PMPS. If it doesn't have a big PT with multiple secondaries and weighs nothing, it probably is. Maybe not, but usually. IMHE... Most power amp units will work stand alone. (But that does mean this one does.) Especially if it has a power switch. And you my be right about protection. If your friend shorted some speaker wires and fried an output device, it may not power up. BUT it would try to quickly before it detected the over current condition.

[J M Fahey]

I suppose itīs a typo for SMPS: switch mode power supply, Iībe heard them being called pulse mode power supply which is also correct, just not that much used.

In any case, there is no conventional power transformer on that unit (which would make it some 5 kg heavier than now) but a big honkin` SMPS inside that RTP1M thingie, the square metal box in the middle.

The fact that it is fully enclosed means that:
* IT CAN KILL YOU because it works with live mains voltage
* it radiates its of interference

very similar to a computer power supply which is also enclosed, fan cooled and deadly.

At least get that full schematic and service manual, even with it these are somewhat complex for a Tech.

In any case, it *might* be working fine, just self protecting because of an amplifier failure; they also need the rest of the system hooked up to even start, this is what a UK seller said:

Seller: vladimirs020 (519) 99.3%, Location: Chesham, Ships to: GB, Item: 162188303014 Rare used ,Technics BI - WIRING AMPLIFIER SU-CH9 (Japan) in full working order That unit from CD System Stereo SC-CH9 & andthis unit only works when connected to ST-CH9+SL-CH9+RS-CH9 +SB-CH9

But apparently your friend had it fully connected and yet it stopped working, so ....
Tell him to buy the schematic, and then give it a go, although it may very well be a complex repair.

[rabbit@]

Hi Juan,

well , I looked up SMPS and the explanation went way over my head I'm afraid.

I just downloaded 79 pages of manual but no schematics on it.
I will get the rest of the system first and hook them all up. she's lost the remote too!! anyway . she can either pay for the service manual or I will take it too the tip if I have no luck.

sorry about not supplying the schematics. I will post if that happens and hope you guys are still interested .

Thankyou for the help from across the atlantic .
Cheers

[rabbit@]

ok got the schematics

technics_sh-ch900.pdf

[nickb]

[ATTACH]41272[/ATTACH]

Well done

No SMPS you'll be glad to know. First place to check would be the power supplies. I'd expect about 10VAC wrt ground on each of TP701 and TP702. If that is OK then start checking the DCV on the transistors in the power supply snippet below - it you look carefully you'll see expected voltages.

Snippet 1.pdf

[rabbit@]

Hey Nick,

ok will give that a go. thanks man .

[Enzo]

yes, that looks like a transformer under that metal cover. You can see the two row of winding end pins soldered to strips of pc board. A fuse on the one board is visible.

[J M Fahey]

Well, thatīs a WEIRD power supply if I ever saw one.

1) To begin with, the points caller "AC" on the snippet, are shorted by series connected 3300uFx16V electrolytics: C703 and C704
That they are actually DC points is confirmed because the top one is connectedb to D701/702 cathodes and the lower one to D702/703 cathodes, so TP701 and TP702 must be fed power transformer secondary voltage.

2) problem is, visible PT701 is NOT the power transformer, but an auxiliary one, with primary fed 23.8VAC and 30.2VAC and 5.4VAC secondaries.
Where is the actual PT?
Probably in some other unit, so if not present , unit wonīt power up.

I was cheated by the square metal box inside, now I guess itīs not an SMPS but yet the main PT is not there.
Letīs keep searching.

OK, that schematic is VERY incomplete , only shows pages 8 to 16 out of 29 total and that only for the SH-CH900 module, we are missing full RS-CH900 , SL-CH90 , SU-CH900 , and even cabinets SB-CH900 ; the actual power transformer might be in any of them.

Weird stupidly complicated design, I bet they did it that way "just because they can"
Only element I do not suspect is the Remote Control

Do you have the full system schematic?

From your back panel pictures:
The Tuner ST-CH9L which isnīt even shown on the manual full system picture, seems to receive 220VAC from 8 shaped 2 pin connector and send "something" to SU-CH9

The SU-CH9 "stereo integrated amplifier" seems to again receive 220VAC and feed SL-CH9, RS-CH9 and ST-CH9 through those weird multipin flat connectors.
Not your exact system but shows their design "philosophy".

I bet an Authorized Technics Service shop can repair it, having access to full documentation and, if needed, special parts.

All others will have a rough day, to put it mildly.

[nickb]

Juan - I think you may be getting fooled by the very badly placed "AC" text - it's very misleading. It's a truly horrible schematic.

They often have a block diagram to help you find your way around. Is there more to the SM that we're not seeing?

[Enzo]

Typos. Reverse positions for posts AC and post TP701,702 on the print. Now the AC from the PT comes into the rectifiers at points AC, then on the DC side of the rectifiers, the TPs make sense. PT701 is just an aux transformer for a low voltage, and its primary is parallel across what should be the AC points. The actual PT is off JK101, note pins 1 and 5 are the affore mentioned AC points and pin 3 the CT.

And yes, of course what we see is incomplete.

[g1]

The SH module is the processor, the SU module is the amplifier.
The system will not power up unless all modules are connected.

[rabbit@]

power up!!

The SH module is the processor, the SU module is the amplifier.
The system will not power up unless all modules are connected.

Hi Everyone. Got some news for you on the amp if you are still interested. Sorry about the wait but I had to pick up the other modules last night and
hooked them up this morning. Amp comes to life again. So, G1 you were right about needed all modules but why it has never fired up until now is a mystery.
Perhaps all my fiddling with fuses did something. loose contact who knows. I was hoping for a bit more of a challenge and a few lessons off the wizards on here but not this time. Apologies for the crappy schematics too. next time I will arm myself with the right data before posting for help.

Thank you all for the input . I appreciate it .

Cheers
Paul