CA400 integrated amp issues

Hello, I recently bought a CA400 that is having trouble:

1) LH channel works but is fuzzy and distorted

2) When the power is switched off the amp motor boats/rumbles for about a second or two

I cleaned the volume control pot with Deoxit and there was some improvement, but I think I have larger issues. I checked all the fuses and they are the correct values and functioning. I have a bunch of test gear but I'm usually working on tube gear, so would appreciate any help as to where to start looking.

Thanks in advance.

2) When the power is switched off the amp motor boats/rumbles for about a second or two

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There is no speaker protect relay circuit. So what your hearing is the main filter cap discharging after power down.Most likely a normal shut down occurance.So either switch speakers off or volume at min. during shut off.
First thing I'd do, is go through and deoxit all of the controls and switches. Most likely that in itself will clear up most of your issues.

I had all sorts of intermittents with mine. Make sure that you do a thorough job cleaning the input and tape switches and the connections from the board they sit on to the rest of the amp. These last connectors seemed to cause mine the most grief. Also mine had a few dodgy solder joints after this time so they will be worth investigating too.

I've cleaned all the pots and switches a few times and found a poor connection at the brown wire carrying B+ from the Tone Control board to the Main Amp circuit board. The second item was found while cleaning so I wasn't able to check the progress in separate steps as the wire broke off at the insulation at the TC board end. I think it was due to poor insulation stripping as the MA end had most of the strands cut so I fixed up both ends.

Now however there is static coming through both channels. The static volume goes up and down with the volume control and is right there along with the audio program being played. The source doesn't appear to be the problem as I've tried different sources with the same results. The sources are quiet through my main audio system.

I recently bought a Tek 2246 scope which I'm learning how to use. I have an old Heathkit AG-10 Sine/Square wave gen and apparently my just new to me Sencore SG165 also has that feature. Is there a way to isolate the source of the static or should I just keep on cleaning the pots/switches?

Maybe I've dislodged something which is now affecting both channels until I get rid of the offending dirt/debris//build up? This unit was never exposed to cigarette smoke.

The remaining cabling/solder connections look good.
There are no obvious signs of capacitor swelling or leakage.

If the static is in both channels.Id be looking at the power supply.(common to both channels) Solder connections,diodes,transistors and capacitors.

TR701 and 702 and associated circuit components.
http://sportsbil.com/yamaha/ca-400-sm.pdf

Thanks avionic for prodding me to poke around the amp. I cleared up another issue and I think I found the problem.

1) Voltages around TR701, TR701, and TR703 were with 0.5v which is close enough for me. However, when I poked around a bit further I noticed power at TR715 was 7.5v which is much lower than the spec'd 26.0v. Further checking found that the fuse (F702) was defective/broken internally and not passing full voltage. When I originally checked it I used a simple fuse checker which probably just confirms continuity. Well there was continuity but not at full voltage so a replacement fuse fixed the left channel.

2) After fixing the fuse and while listening to program material and static in the right channel I starting probing around with the ancient Chinese secret ... a nice long chop stick which I use for probing high voltage tube circuits. I was tapping things, moving wires and then finally I was scratching the top of TR716 and noticed more static. I removed the amp from my system and measured the voltage at TR716. It was all over the place as I touched it with the chopstick. So, either I have a bad solder connection or bad transistor. I'm not at all familiar with transistors to know if they fatigue internally but continue to work.

So now a few questions:

1) Since I have to pull the circuit board to check TR716, should I just replace it (and the other three 2SC1509 transistors)? Is the Q~R suffix on the parts list significant?

2) Is there a better transistor than the spec'd 2SC1509?

3) Should I upgrade/replace any of the other transistors on the main board?

4) C711 and C712 appear to be 0.68uF/35v Tantalum caps. Is there any advantage to change them to film caps? Would the bass response be improved if the value is upped a little? I only have 400v and up caps for these small values, is that OK?

5) Other than the e-caps, are there any other preventative maintenance or improvements to the main board?

6) Is there any advantage to upping the value of the 4700uF/50v PS caps? Maybe bypass with some 4.0uF/160v MBGO Russian caps? I have a bunch of them on the shelf.

Before any other changes or mods I'm going to resolve the transistor problem then go from there, but any help suggestions are greatly appreciated. Since the amp is more than 30 years old I'm also going to replace all the e-caps on the main board once the static issue is resolved.

2sc1509
512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

double check the pin out..
Noisy transistors usually test good. The best way is to just replace suspected trouble makers.

Thanks avionic.

I was checking Mouser and they no longer carry KSC2383YBU, so I'm wondering if the following would be a suitable substitute:

KSC2383YTA

While I'm at it, I'm wondering if I shouldn't replace the following transistors on the main board (for which I would need current or substitute numbers):

2SC458C
2SA561 O~Y
2SA763WL4~5
2SC458LGC or D
2SC458B~C
2SA777Q~R
2SC1061SB~C
2SA671SB~C

I checked a few of these and they were either NLA or didn't show up at all. I do all my own work, so it's just my time since I may as well make the shipping cost worth my while.

If these were vacuum tubes I'd know which ones I needed!! LOL

KSC2383YTA

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Yep same transistor...512-KSC2383Y The TA means Ammo tape packaging for automatic machine insertion . BU meant Bulk (loose pieces)packaging-- TU means tube packaging..

All 2SC458's --> 512-KSC1845FTA
2SA561 >> 512-KSA733CYTA
2SA763 --> 512-KSA992FBU
2SA777 -->512-KSA1013YBU
2SC1061 -> 512-KSC2334YTU
2SA671SB~C-->512- KSA1010YTU



As with all transistor substitutions double check pin out old versus new..

Thank you very much avionic! That's very helpful and thank you also for the pinout reminder.

Well, some good news and some bad news.

I was putting my parts order together yesterday afternoon and decided to lift the main circuit board to check for signs of capacitor leakage. There was none, but I noticed that two of three pins of transistor TR716 were poorly soldered with one of the pins still loose (ie. not soldered to the board).

The good news is I soldered the pins to the board and TR716 is quiet when prodded with the probe; the bad news is the static remains in the right channel.

I plan on ordering replacement transistors to replace all of them on the main board until at least the issue is resolved, but I'm wondering if there is a way to isolate the source of the static to that board or another since the voltages all seem to be correct. Or do all signs still point to the main board -> the volume of the static increases with the volume control.

I don't have a signal tracer, but do have a Tek 2246 scope and various pcs of (vintage) test equipment for tube gear.

Do you hear this noise through headphones as well ?

I don't have any head phones.

Can I use a 1/4" microphone plug to connect an efficient speaker to the head phone jack?

Tom_r said:

I don't have any head phones.

Can I use a 1/4" microphone plug to connect an efficient speaker to the head phone jack?

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Have you tried both speaker A and B connections ?

Well avionic, a funny thing happened on the way to ....

I connected a pair of speakers to the B output, and fired everything up. It started out with the usual static for about 5 seconds, paused for a second, then voila! the static was gone. I connected another pair of speakers to the A output and everything is working as it should.

I'm wondering, could the correction of the cold/bad solder joints on TR716 have caused a capacitor to reform allowing the RH channel to work properly. I only played it for maybe a minute yesterday after re-soldering the transistor.

I'm going to be gifting this amp to someone so I want to be sure it's working properly. Could there be anything else I should be checking?

Tom_r said:

Well avionic, a funny thing happened on the way to ....

I connected a pair of speakers to the B output, and fired everything up. It started out with the usual static for about 5 seconds, paused for a second, then voila! the static was gone. I connected another pair of speakers to the A output and everything is working as it should.

I'm wondering, could the correction of the cold/bad solder joints on TR716 have caused a capacitor to reform allowing the RH channel to work properly. I only played it for maybe a minute yesterday after re-soldering the transistor.

I'm going to be gifting this amp to someone so I want to be sure it's working properly. Could there be anything else I should be checking?

Click to expand...

Deoxit the speaker select switch several times this weekend..:thmbsp:
That and look over the wiring to the switch for broken iffy wire connections.:scratch2:

Thanks avionic for all the help. I will do that.

What is it with the poor QC with older Yamaha?

And to think I bought a TOTL Yamaha integrated amp IIRC ??1010 around 1982 which I threw out because it wasn't working when in fact it may have been a simple fix. :sigh::sigh: I also bought the TOTL tuner that went with it and threw it out for the same reason!!

Tom_r said:

Thanks avionic for all the help. I will do that.

What is it with the poor QC with older Yamaha?

And to think I bought a TOTL Yamaha integrated amp IIRC ??1010 around 1982 which I threw out because it wasn't working when in fact it may have been a simple fix. :sigh::sigh: I also bought the TOTL tuner that went with it and threw it out for the same reason!!

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Nothing lasts for ever,Thats what keeps old fart techs busy..This gear is pushing 40 years old. Metals oxidize,heating and cooling cycles take there toll. Enviornmental conditions vary. Shit happens..

avionic said:

Nothing lasts for ever,Thats what keeps old fart techs busy..This gear is pushing 40 years old. Metals oxidize,heating and cooling cycles take there toll. Enviornmental conditions vary. Shit happens..

Click to expand...

LOL ... that's why we can find vintage gear at bargain prices.

BTW, although no longer in production Gravely 2 wheel tractors are made to last multiple lifetimes. Gravely is now owned by Ariens, their previous owner lasted further into the 20th century as the owner of Gravely than as a manufacturer of automobiles - Studebaker. They sold Gravely in the late 70's. The original 'gravely' engines starting in the 1930's and made well into the 70's featured such things as pressurized oiling system, oil pressure gauge, oil filters, etc.

Anyway, back to the Yamahahahaha's.