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JVC AX-1 recap, help needed with noisy phono stage

leesonic

leesonic

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I just re-capped my JVC A-X1 amplifier today, it took a lot less time than my Pioneer SX-535. As with the Pioneer, I used Nichicon caps, except for the main power supply ones where I had to use Panasonic.

JVCAX1recap-01.jpg


JVCAX1recap-02.jpg


Here is the phono board before and after pics.

JVCAX1recap-03.jpg


JVCAX1recap-04.jpg


Here is the main board before and after pics. I had to drill new holes in the board for the main caps, as the pin spacing was slightly smaller.

JVCAX1recap-05.jpg


JVCAX1recap-06.jpg


One thing I am still having a problem with is a noisy phono stage. It has a noisy left channel, I was hoping the re-cap might have cured it, but it didn't. It sounds almost like white noise, there seem to be all frequencies there. It reduces a bit with a turntable plugged in, but it's still there. I have tried removing the wires from the RCA jacks with no change, and also swapping the output wires from the phono board to the main board, the noise then goes across to the other channel.

I was looking at the schematic (below) to try and figure out what's wrong? I hope it's not a problem with the Hitachi HA1452W chip, as these don't seem to be available anymore.

Anyone got any bright ideas?

Lee.

JVCAX1phono.jpg
 
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take it you have cleaned the switches ? failing that a cold solder joint or poor connection somewhere may be a suspect ..but seeing you have worked on the board you may have noticed . ..in have loads of chips but cant say if i have that one ...its too late for me to go looking right now
 
It's probably the chip. If replacements are extremely scarce, then consider kludging an industry-standard dual audio op-amp (e.g. 5532) in its place. C315 & C316 wouldn't be used, but I suspect everything else would work as originally designed. Make sure none of the lytics are reverse-biased after you do this.
 
I ran a quick check on Mouser for that chip. It led me to a replacement NTE unit for $5. They had about 80 in stock.
 
petehall347 said:
take it you have cleaned the switches ? failing that a cold solder joint or poor connection somewhere may be a suspect ..but seeing you have worked on the board you may have noticed . ..in have loads of chips but cant say if i have that one ...its too late for me to go looking right now
Click to expand...

Cleaning the switches - first thing I did. I re-flowed all the solder joints on that side of the the phono board, still had the same problem. I'd appreciate it if you could have a look for one of those chips when you get the chance.

BinaryMike said:
It's probably the chip. If replacements are extremely scarce, then consider kludging an industry-standard dual audio op-amp (e.g. 5532) in its place. C315 & C316 wouldn't be used, but I suspect everything else would work as originally designed. Make sure none of the lytics are reverse-biased after you do this.
Click to expand...

That would be plan C after all the other options are exhausted.

JamesDean59 said:
I ran a quick check on Mouser for that chip. It led me to a replacement NTE unit for $5. They had about 80 in stock.
Click to expand...

Doh! (how come there's no Smiley for that?) Didn't think to even check Mouser, and that's where I bought the caps from. I will try that next time I make an order.

See what you've done? This JVC re-cap only came about because I had to order two more capacitors for my Pioneer SX-535 re-cap, and I hate making orders for 25 cents when the shipping is $10. Now, what do I have in the basement that needs re-capping? A Kenwood KT-7500... hmmm :scratch2:

You guys are great! :thmbsp:

Lee.
 
Just curious, did you check the old caps, and if so were any of them out of spec?

I've recapped a few units, only to find nothing wrong with the old caps. Notable exception was a Bose 901 Series 1 EQ, in which ALL the caps were out of spec (it still worked though)

and yes I know that electrolytic caps should be replaced after 30 years or so. It was just an observation...
 
Here is the phono pre-amp board with a new gold-plated socket installed, waiting on the replacement chip to arrive from Mouser.

JVCAX1recap-07.jpg
 
Good to see a classic properly restored!
It would be very interesting to know something about the sound/performance of this particular model:how does it sound compared to other amps?
Jvc amps aren't widely known so it would be nice to know a little more.:scratch2:
 
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