The Sharp VZ-3000 is back, and this time it's getting FIXED !

Hi all,

Some of you may remember my previous postings about my Sharp VZ-3000 'both sides play linear tracking' record player boombox. I know it's not a portable unit but it still received a warm welcome here when I initially posted it so now I'm back !

Some months ago, I decided to sell the VZ because it was getting frustrating trying to work on it. A local guy bought it off me and I carried on with other stuff. Recently however, I.ve been getting more into component level repairs and learning how to solder and use an oscilloscope. I began wishing I had kept the VZ because now I may be in a better position to fix it.

Fast forward to today and it is back in my possession, exactly as it left me. The guy who bought it contacted me recently to ask if I might want it back - he took it to his work to have a look at it but got busy and never did anything with it. I said sure, I would take it back as long as it was complete. He said it was and that he thinks he traced the fault with the sound output to an issue in the EQ board. He also told me the speakers needed refoaming - I never looked at them myself.

So here we are, the VZ is still mostly stripped down to the bare chassis. The PSU is fitted, main control board, tape deck / board and tuner are all connected. My plan is to inject a 1Khz tone through the AUX input and attempt to trace that through the unit using my scope until I find the point where it cuts out. This will be my first attempt to actually use a scope to trace out a fault so I will keep this thread updated with my progress......

An interesting story that is developing well, good luck with the resto.

Very cool. Hope you find the issue.

We all have at least one boombox we regret selling or trading. You got lucky and have a second chance. You know what this reminds me of?

Hey thanks everyone, it's good to be back among you friendly folks here on Boomboxery

I've found the source of the loud hum and it turns out it's the STK463 power amplifier pack. When I was contacted by the guy who bought this thing off me, he said the power amp was fine ! What he didn't do is check for DC current on the speaker outputs, a number one cause of hum (and fried speakers !!). I found 30 vDC on both left and right channels so hardly surprising I had hum......

I pulled the pre-amp connection to the power amp and found I still had big DC on the outputs, so my issue was the amp or the PSU. I found a pin out for the STK463 package an checked the left / right channel output pins and sure enough, I had full DC rail voltage on both. The only conclusion from there was that the STK is bad, so I ordered up another one from a local supplier

I got the old chip package desolered this morning, just waiting on the new one to turn up. Happily, I've found that the cassette deck and tuner both work and all the drivers in the speakers are OK and not frazzled from having all that DC going into them. They just nee some new foam round the woofers - easy job.

Once the new amp chip is here, I need to fit that an then think about trying out the record player unit.....

If I may suggest one thing. If the voltage over speaker was negative, please test the 0.33 ohm resistor between pins 6 and 7 or 10 and 11. If this resistor is not soldered proprely it could produce negative voltage, and hum. It is unlikely that this resistor is blown, but...

Have a nice day!

Hey thanks for the heads up. I've been through all resistors on the amp board and they measure good (except R417 which is 100 ohm 1/4 watt fusible).

I have the new IC fitted, but may remove it again and replace all the electrolytic caps and double check all resistors.

I'm going to replace the R417 with a 1/4 watt carbon film just for testing as I cannot find a local source of the original type spec.

I will check those output voltages, I think they were -ve.

Actually, I was initially injecting a 1khz sine tone into the amp and I could trace it all the way to one of the resistors. Can't remember which resistor, but on one side I heard the tone (with my home made audio probe) and on the other side of it I heard just noise. Maybe I found a problem and just forgot to investigate it further !

Actually I only see 3.3k and 33k resistors in the circuit. The only .33 ohm resistors are within the STK and I can't solder those !

Well I replaced all the caps in the power amp and replaced the suspect fusible resistor and I now have SOUND !

Still a bit of DC hum hiding somewhere, could be a missing ground or I may need to recap the preamp too (might do that anyway).

Well, what a mission this turned out to be. After recapping the power supply and power amp and fitting a new STK I ended up with a quiet right channel which distorted with increasing volume.

I checked all my work and the only thing I could think of is perhaps the new IC is bad. Luckily I kept the old one so I put it back in and amazingly, it worked perfectly ! Both channel even, good strong sound.

I think this goes to show there are many wrong turns on a diagnostic adventure like this one ! Noe to get the record player going again !!

yes i have a 3000 sitting up in the roof i must get down some day and fix

Good to hear! So the new amp chip worked better before the re-cap/new resistors and the old amp chip works better afterwards?
Just goes to show how interconnected problems are, and trying to place blame correctly!
You'll like this http://conradhoffman.com/troubleshoottut.htm

I went with replacing the IC (foolishly) before I had replaced the caps on the amp board. Had I done the caps first, I would have found the IC was working fine - lesson learned (and 32 pins soldered / desoldered !!)

I'm now digging into the record player and problems are springing up all over the place. Two of the three micro switches on the back of the player and totally broken and need replacing. One of these is the 'door open' switch and the other is the 'tone arm rest position' sensor. I'm not surprised the player isn't working because currently, it thinks the door is always open and the tone arms are never at rest !!

I need to replace the tone arm / door drive belt because the old one is totally hardened and I also need a platter drive belt, so I've ordered a kit off Ebay for that. I also ordered a pack of six mini micro switches, after receiving great info from a fellow member of Boomboxery.

Whilst I'm waiting for these orders to arrive, I will probably recap the player PCB (there's a dozen or so electrolytics to do), probably recap the speakers (one cap in each) and fix the foam woofer surrounds. Should keep me out of trouble (or get me in to it, with the wife).

Keep rocking !

Well the new parts have arrived in super quick time ! I did recap the player board, but haven't touched the speakers.

I've got the belt kit fitted, now I just need to replace the two broken micro switches....

Sounds like you know what you are doing. I am sorry for my (wrong) input about resistor, I was probably looking at schematic that differs from your device. I could only blame me and the internet for it.

So, the conclusion is that the capacitors were bad and that produced overcurrent and blown the fuse? What is the conclusion, what was wrong on both channels? Not that I want to bother you, just that I was "burned" by not getting to the bottom of the things before. The distortion can be caused by leaky cap, but those amps should be pretty insensitive to that. What is the AC ripple of the PSU? Noisy and distorted sound can be caused by leaky cap in the stage before the potentiometer... usually somewhere between 1 and 10 uF, 10-16V. If this one is bad/leaky, there is no need to replace them all.

Anyway, keep up the good work, and good luck!

HRmeteohub said:

Sounds like you know what you are doing. I am sorry for my (wrong) input about resistor, I was probably looking at schematic that differs from your device. I could only blame me and the internet for it.

So, the conclusion is that the capacitors were bad and that produced overcurrent and blown the fuse? What is the conclusion, what was wrong on both channels? Not that I want to bother you, just that I was "burned" by not getting to the bottom of the things before. The distortion can be caused by leaky cap, but those amps should be pretty insensitive to that. What is the AC ripple of the PSU? Noisy and distorted sound can be caused by leaky cap in the stage before the potentiometer... usually somewhere between 1 and 10 uF, 10-16V. If this one is bad/leaky, there is no need to replace them all.

Anyway, keep up the good work, and good luck!

Click to expand...

Hey, no worries man ! I've had my fair share of wrong turns on this one so it's all good.

I'm at the point now where I have record playback (woohoo !!) but only on side B :-( I've messed around with the tonearms etc but I cannot figure out why the side A arm will not advance. I think I may have found an issue with the photointerrupter on the arm, which sends high / low voltages via an OPAMP to the drive motor. It looks like the drive signal is always low, so I need to trace that out. I hope the interrupter itself is OK an it's an issue with a resistor or diode somewhere.....

The other thing worth mentioning, when you asked about the conclusion, is that this unit had previously been switched on 240v mains with 110v selected on the back. Personally, I have no idea what kind of damage that could have done but most of the issues I've found could be related to that. I'm glad to say it wasn't ME who set the power wrong, I'm just fixing the mess !

I've tracked down the cause of side B only playback - there are two pair of transistors which control side A / B tonearm solenoid operation and when a solenoid is energised, the tonearm position sensor on the opposing tonearm is switched off. I found that one the side B transistors was bad an was switching the side B solenoid as soon as the unit was powered up, thus also cutting out the side A position sensor.

I had a bit of trouble finding a replacement transistor locally, because they are the Japanese standard ECB arrangement but I've found a source of them now. I'll report back once that is swapped out an see if we have A an B playback fixed !

Got some replacement woofer foams sorted for the Sharp today - didn't have sufficient glue to finish them, so I'm going to put the new components in the player tomorrow and then look at finishing the speakers probably by the end of the week. If all goes to plan, I should have this finished an all back together by the weekend. On to the next project then - two vintage Sony silver face amps from 1972 !!

Success !! Replacing one tiny little $1 transistor has enabled side A and B playback, repeat, continuous etc !

BUT....another problem now presents itself. There's a relay which switches cartridge signal paths between A and B and I've found that sound output form A is much weaker than from B. As all the other components in the signal path are common, I figured I could have dirty contacts in the relay. I opened up the relay and tried cleaning the contacts with some cleaner soaked into a business card, but it seemed to have little effect.

This relay, a Fujitsu 221D012, is pretty hard to find and there's no direct replacement that I'm aware of. I managed to find some original units in the US, so I've ordered a couple (to meet minimum order requirements). I will report back once this relay is fitted !

Some hardcore debugging action here, you're going to have this thing licked soon!
Where did you find the relays at?