Jump to content


Photo

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


  • Please log in to reply
27 replies to this topic

#1 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 14 March 2017 - 02:25 PM

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......



#2 MyOhMy

MyOhMy
  • Members
  • 1,684 posts
  • LocationSleaford, Lincolnshire, UK.

Posted 14 March 2017 - 11:52 PM

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



#3 baddboybill

baddboybill
  • Boomus Fidelis
  • 12,645 posts
  • LocationIn the middle of nowhere!!

Posted 15 March 2017 - 05:51 AM

Very cool. Hope you find the issue. ;-)



#4 Fatdog

Fatdog
  • Administrators
  • 10,940 posts
  • LocationMiddle Tennessee, U.S.A.

Posted 15 March 2017 - 10:05 AM

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?

 

 

64586917.jpg



#5 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 16 March 2017 - 05:19 PM

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.....



#6 HRmeteohub

HRmeteohub
  • Members
  • 40 posts
  • LocationCroatia

Posted 23 March 2017 - 01:43 AM

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!



#7 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 23 March 2017 - 09:27 PM

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 !

#8 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 23 March 2017 - 09:41 PM

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 !

#9 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 24 March 2017 - 01:17 PM

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).

#10 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 31 March 2017 - 11:55 PM

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 !!

#11 nz boom

nz boom
  • Members
  • 1,480 posts

Posted 01 April 2017 - 04:05 AM

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



#12 caution

caution
  • Members
  • 1,156 posts
  • LocationHillsboro, Oregon

Posted 01 April 2017 - 12:25 PM

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...bleshoottut.htm



#13 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 04 April 2017 - 04:13 PM

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 !



#14 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 11 April 2017 - 01:28 PM

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....

#15 HRmeteohub

HRmeteohub
  • Members
  • 40 posts
  • LocationCroatia

Posted 12 April 2017 - 09:14 AM

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!



#16 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 12 April 2017 - 02:50 PM

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!

 

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 !



#17 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 14 April 2017 - 06:39 PM

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 !



#18 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 15 April 2017 - 11:52 PM

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 !!



#19 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 17 April 2017 - 03:48 PM

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 !



#20 caution

caution
  • Members
  • 1,156 posts
  • LocationHillsboro, Oregon

Posted 17 April 2017 - 04:41 PM

Some hardcore debugging action here, you're going to have this thing licked soon!

Where did you find the relays at?



#21 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 18 April 2017 - 12:56 PM

I found the relays at RFParts in the US. They have limited stock so I grabbed two.

If for any reason there's a problem getting them, the relay can be jumpered out but I'd rather not do that because it does provide muting of the tone arm which is not in use. I suppose I could try a jumper whilst I'm waiting for delivery, see how it sounds....

#22 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 19 April 2017 - 12:48 PM

Made a start on refoaming the woofers last night. If these don't work out, or are too far gone, I have a pair of Infinity Reference One bookshelf speakers that I could use. I would probably transplant the drivers and crossovers into the Sharp cabinets because the drivers are the same size, so I could keep the original look.

#23 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 20 April 2017 - 02:47 PM

Well I decided last night that I need to create a 'Frankenspeaker' for the VZ. The Sharp woofers are toasted from having large amounts of DC through them - I tried refoaming, centering the coil with shims, setting it all up nice, but I still get voice coil buzz.

 

Last night, I started experimenting with loading the Sharp cabinets with Infinity drivers and I was pleasantly surprised how nice it sounded. For reference, I had one complete Infinity Reference 10 on the left, and one frankenspeaker on the right. I couldn't really tell much difference, even though all I had done was to put an Infinity woofer in the Sharp cabinet (same size driver, fortunately).

 

I'm thinking about moving the woofers and tweeters over to the Sharp cabinets, cutting a hole in the back of the Sharps to accomodate the Infinity crossovers / binding posts, and stuffing the Sharps with the Infinity wadding. In an ideal world, the front grille of the Sharp speaker would have simply fitted onto the Infinity speaker but sadly that was not to be - the Infinity is slightly taller and narrower than the Sharp box so it would not work out.



#24 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 22 April 2017 - 03:27 PM

The relays for the cartridge signal path have arrived, I will be replacing the faulty one in the next couple of days :-)

#25 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 25 April 2017 - 03:59 AM

Fitted the new relay and the record player sounds great. Now all I need to do get the damn case back together !

#26 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 25 April 2017 - 08:18 PM

Got the case back together - it's a tricky one and it's a tight fit. It's not helped by the fact that you have to fit the case over the record player door, with the door open. In the event you can't open the door, you can't the case on / off !! There's a manual release on the player door, accessed by pushing a piece of rod through a hole on the top right corner at the back. If the gear solenoid is jammed with the gear in 'tonearm' position though, that sucker isn't going to open.....



#27 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 30 April 2017 - 04:45 PM

After reassembling the unit, at least partially, I suddenly had another problem ! The tape level meters were registering sound, even though no tape was playing, and there was random interference coming through on all inputs which sounded like someone blowing into a microphone.

 

I tracked this down, I think, to the tape deck erase head. I disconnected it from the main board and the level meters settled down to zero. I also don't hear the blowing / popping sound any more. I'm not bothered about the record function of the deck as I will never use it, so I've left the head disconnected for now.

 

Now it's on with modding the speakers !!!



Here's a pic of where I'm at with the thing :-

 

Attached File  IMG_20170428_073708.jpg   59.73K   0 downloads

 

 

 



I've just realised my disc illumination and cartridge illumination lamps don't work. Hopefully, its just the lamps that need replacing because I really don't want to drag this thing apart AGAIN......



#28 markoneswift

markoneswift
  • Members
  • 267 posts
  • LocationAotearoa New Zealand

Posted 03 May 2017 - 08:11 PM

A few more piccies npw reassembly is nearly one. Just need to polish up the dust cover now.....

 

Attached File  IMG_20170504_095932.jpg   72.43K   1 downloads

 

Attached File  IMG_20170504_095949.jpg   45.76K   0 downloads

 

Attached File  IMG_20170504_100001.jpg   77.92K   0 downloads

 

Attached File  IMG_20170504_100023.jpg   72.87K   0 downloads