Sanyo Plus P55 Power Amp

[Socal Sam]

Check out my Sanyo Plus Series P55 power amp. Despite the small size and BPC styling, it has some serious guts.

Dual mono design
Dual TKK transformers
Two pairs of 63v 10,000uF main filters
Two pairs per channel Hitachi 2SJ49 and 2SK134 Mosfet outputs
Freon cooling tunnel for the Hitachi's
Relay operated speaker selector with one relay each for A and B speakers

With 20,000uF per channel, the 100 wpc rating is conservative.

[BroonsBane]

Nice Sam. I had the matching preamp at one point. Sold it and have regretted it since.

[Scorpion8]

Check out my Sanyo Plus Series P55 power amp.

Sweet nudies! Thanks.

[Socal Sam]

Nice Sam. I had the matching preamp at one point. Sold it and have regretted it since.

I have a complete set with rack ears. The preamp is decent enough. The tuner is special and like the P55 has dual power supplies, one for the analog output and one for the digital tuner. I'll open up my T55 and post a nudie.

[Socal Sam]

I was giving the P55 a good workout last night and I heard a soft gurgling sound coming from the P55. That's the freon circulating inside the tube. It sounds just like an air conditioner unit. No worries, the gurgling is inaudible with music playing.

[Patrick]

Hello everybody, My name is Patrick and I am from South Africa and I am new to your forum and I have joined in the hope that somebody can help me.
I have a Sanyo Plus system which dates back to 1983 when I purchased it new. The set comprises of the P55 amp, The separate pre amp, the digital tuner and the programmable tape deck.
This unit has run all these years delivering incredibly clean and powerful sound which in my opinion is comparable to the best available even today.
Finally it has given up the ghost, and the local agent tells me that it was discontinued 18 years ago and they can't help me. We do not have competent technitions available for this kind of equipment here and there are no service manuals or schematics available. Please can anybody help with this documentation?
I have opened up the amp as this is where the puff of smoke appeared to emanate from and I found a 1 amp bridge rectifier well and truly cooked. Also several solder joints which have deteriorated over the years. I have replaced the bridge and repaired all the joints. Also I have stripped all the switches and serviced them and confirmed that they are all functioning correctly. The main on/off switch and the speaker switch have been a bit dodgy for years but they are now in good shape again. I have tested both transformers and both function correctly. When I power up the amp, all the leds on the front panel light up and stay lit up and the protector circuit doesn't switch off. Please, if anybody can offer advice or sugestions on the repair of this amp, I would be most grateful as it would break my heart to trash such a superior piece of equipment which I have become very attached to.
Thank you. Sincerely Patrick

[Socal Sam]

Patrick: Great amp. You will want to remove the output transistors and check them. Suspect one or more are open. After replacing them, power up with a dim bulb tester or a variac so you do not blow your new transistors. Sorry I can't be more specific but this should get you started. Good luck!

[Patrick]

Dear Social Sam
Thank you very much for your reply. Are you refering to the 2SJ and 2SK mosfets or the transistors on the other boards. The mosfets are the only parts that I havn't checked yet. If you ever stumble across a service manual or a schematic for this amp I would really appreciate a copy.
Thanks again for the king assistance, I am very grateful for your inut.
Regards Patrick

[Warped Bezel]

Dear Social Sam
Thank you very much for your reply. Are you refering to the 2SJ and 2SK mosfets or the transistors on the other boards. The mosfets are the only parts that I havn't checked yet. If you ever stumble across a service manual or a schematic for this amp I would really appreciate a copy.
Thanks again for the king assistance, I am very grateful for your inut.
Regards Patrick

Please feel free to use the link for Njord Noatun's scans as they are provided to Tapeheads members and if you have paper manuals or brochures that you might be able to provide let him know and he may be able to add them (I think he's backlogged but he will tell you when it's time).

[Socal Sam]

Dear Social Sam
Thank you very much for your reply. Are you refering to the 2SJ and 2SK mosfets or the transistors on the other boards. The mosfets are the only parts that I havn't checked yet. If you ever stumble across a service manual or a schematic for this amp I would really appreciate a copy.
Thanks again for the king assistance, I am very grateful for your inut.
Regards Patrick

Patrick, IIRC the P55 is dual mono. So, if you disconnect the amp modules the relay should click because it no longer detects a short. Then reconnect the left and the right individually and you should be able to identify which channel is blown. This is very simple diagnostics, there is a lot more to amp repair than this.