SP10 Troubles

Love it or hate it, it just won't stop
Max N
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Post by Max N » Sun Mar 18, 2012 10:30 pm

Pretty busy yes. Plus I have distracted myself a bit by deciding to design a tonearm - don't laugh.

RussellS
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Hello there. Please help me stop crying.

Post by RussellS » Wed Oct 03, 2012 11:59 am

Hi, I'm new.
I have a love of old and new HiFi, and a major problem. First a little about my sound stuff.
I have a Technics SL1200 Mk2 turntable for daily use (and it is USED daily).
Sony and Panasonic surround sound amplifiers about 1200 watts,
Home-built loudspeakers based on a Wharfedale design with frequency response down to 16Hz.
Akai GX4000D reel tape recorder/player.
Technics Cassette recorder/player.
Sony PS3 for DVD, BluRay and 3D TV.
LG VHS player.
Sony and Philips graphic equalisers.
Plus a home-built pair of Mullard 5-10 amplifiers with with twin 3 valve pre-amps for special Hi Fi.
And a shed load of mixers, pre-amps, decoders, etc.

BUT, here's what kept me awake on Saturday night. I shorted the 5v rail on my Technics SP10 Mk2 to the 32.5v rail - whilst debugging cogging on 78rpm - and the the TTL logic board is essentially now a 5 watt heater. I saw Nick had a similar disaster (for that is what it is) and have emailed him.

Can anyone else give some hope?
I either do, or I don't. There is no 'try'.

RussellS
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Post by RussellS » Wed Oct 03, 2012 12:08 pm

I have read earlier posts and I want to cry - again.

About eight years ago I moved house and looked at my heavy Garrard 301 turntable and the decline in vinyl and decided it had to go.

So I JUNKED it. I can't believe I was so stupid...
I either do, or I don't. There is no 'try'.

Neal
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Post by Neal » Wed Oct 03, 2012 3:07 pm

There are some thread on Vinyl Engine that may help, like this one:

http://www.vinylengine.com/turntable_fo ... 16&t=49797

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Nick
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Post by Nick » Wed Oct 03, 2012 9:46 pm

Ok, lets see if I can remember what I did.

The original IC, use, replacement LS or HCT

SVM530200 Quad NAND 74LS00
SVIM53273 Dual JK Flip Flop 74LS73
SVIM53293 four bit counter 74LS93
SVIM5943 Quad NAND open collector 74LS03
SVIM53204 hex inverter open collector 74LS04
SVIM53210 triple 3 input nand 74LS10

To make it work after that,

change R261 to 1k (different load on driven device)

Add a 22k resistor from IC11 Pin 3 to +5v as its a open collector output (shouldn't work in the original, but they get away with it).

change R221 to 1k different load again

Thats it. Works for me, there is still a odd glitch that happens once every few hours, but not enough to make me look for it. Might be simpiler now I have a digital scope, all teh above was debugged with a analog Tek, and looking for the double triggers was fun :-)
Resistance isn't futile it's V / I.

RussellS
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Post by RussellS » Thu Oct 04, 2012 7:54 am

Nick wrote:Ok, lets see if I can remember what I did.

The original IC, use, replacement LS or HCT

...

and looking for the double triggers was fun :-)
You can't know how appreciative I am. I thought it might be a write-off.
Thank you from the bottom of my heart, and so speedily as well.
I will be buying the components as soon as possible and get on it.
I'll let you know of progress. (It may be slow, I have some birthdays this month). :oops:
I either do, or I don't. There is no 'try'.

RussellS
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Post by RussellS » Thu Oct 11, 2012 1:28 pm

Nick wrote:Ok, lets see if I can remember what I did.

The original IC, use, replacement LS or HCT

SVM530200 Quad NAND 74LS00
SVIM53273 Dual JK Flip Flop 74LS73
SVIM53293 four bit counter 74LS93
SVIM5943 Quad NAND open collector 74LS03
SVIM53204 hex inverter open collector 74LS04
SVIM53210 triple 3 input nand 74LS10

...
I think there are errors in your list. Please confirm (I have added quantities). I am just checking...

SVM530200 Quad NAND 74LS00 - original should be SVIM53200?
SVIM5943 Quad NAND open collector 74LS03 - original should be SVIM5946?

Also, the chips are numbered IC1 to IC16, but there appears to be no IC10 on the schematic diagram (logic circuit). Is this your experience as well?

74LS00 x3
74LS73 x6
74LS93 x2
74LS03 x1
74LS04 x1
74LS10 x2
A total of 15 (see above). Where is IC 10spec?

Thanks in advance.

Russell
I either do, or I don't. There is no 'try'.

Neal
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Post by Neal » Thu Oct 11, 2012 6:14 pm

Its bottom right on the schematic Russell, a 53273P

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Nick
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Post by Nick » Thu Oct 11, 2012 7:57 pm

Yep, typos copying from one window (image) to text.
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RussellS
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Post by RussellS » Fri Oct 12, 2012 8:14 am

Thanks for the help guys. The job is started. I'll let you know how it goes...
I either do, or I don't. There is no 'try'.

RussellS
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Post by RussellS » Mon Oct 22, 2012 2:48 pm

Update:

I laboriously desoldered all 16 TTL chips and cleaned up the holes. A trip to my local electronics store got me most, but not all, of the replacements identified by Nick.

I asked for 16 sockets and got 16 sockets but they were all 16 pin, so I had to 'convert' them to 14 pin before I could solder them in place (I wasn't going to drive back to the shop for such a piddling conversion and there was plenty of space on the board for the extra length).

Because I didn't have all of the chips, I decided to try the old ones one-at-a-time. I rigged an ampmeter to show 1000mA on the 5v line and, one-by-one plugged the chips back in their places. If the meter showed a draw of about 5 to 20 mA per chip I left it there. If it was much higher (50 to 150mA) it was probably blown and I replaced it. For the record, final 5v current draw was about 250mA.

The 7473s seemed to be the most susceptible and I had to replace them all. The 7400s were hardier and I had to replace only one.
The 7493s were both OK and the 7403, 7404 and 7410s were OK as well. Mercifully, they included the types the shop didn't have!

I didn't replace any resistors as it worked as soon as the last chip was in place!!

I had to adjust R101 and R102 pots to stop grumbling on 78 (which it was doing before the 'accident and why I had it open in the first place, I thought it might be failing electrolytics but it wasn't, it was signals out of adjustment) and it seems perfect now.

What a relief - total cost in money was GBP5, in time was about 20 hours, and in life expectancy was about 2 years off my life at the beginning when the spark showed me the short happening.

I have used the opportunity to replace the failing strobe light with LEDs and now have a handsome work of art back in its harness playing records.

Thanks to Nick and all who offered support. :lol: :lol:
Last edited by RussellS on Mon Oct 22, 2012 3:05 pm, edited 5 times in total.
I either do, or I don't. There is no 'try'.

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pre65
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Post by pre65 » Mon Oct 22, 2012 2:51 pm

Well done sir, nice to hear of happy endings. :)
Life is what happens to you while you're busy making other plans. John Lennon

G-Popz THE easy listening connoisseur. (Philip)

Neal
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Post by Neal » Mon Oct 22, 2012 10:43 pm

Yep, +1, well done.

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Post by Mike H » Tue Oct 23, 2012 3:35 pm

Yep +2! Image
 
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Post by RussellS » Tue Oct 30, 2012 10:50 am

Me back again...

Some more experience with the SP10s. I was given two, one in sad condition and the other in fair condition, both without power supplies (no SH10s). I intended to make one good one out of the pair.

I built a power supply using a scrap-box transformer (15-0-15v 2a and 6v 3a) with voltage regulator chips: 5v 1a for the 5v rail and scrap box 20v 1a plus a zener or two and a high power NPN transistor to get voltage up to 32.5v and current up to 3a). A couple of suitable electrolytics on each rail and I was in business. In fact, all scrap-box except the 5v regulator and the 4pin connector. NB. No 140v rail because I was going to replace the failing or dud neon strobe tubes with LEDs.

The first table to go on the bench was the suspected dud.

In my earlier posts I have outlined my accidental shorting of the 5v rail to the 32v rail. 20 hours, 16 sockets and a few TTL chips later...

It responded to additional care but I couldn't get the signals on my scope to line up like the manual when adjusting VR101 and VR102. In fact, I discovered that, when I connected the scope probes (an old Philips dual beam scope) it actually influenced the signal shapes and timings, there must be some probe capacitance/resistance issues. I eventually found that adjusting VR101 while watching the strobe LEDs seemed just as effective (at 33.3 turn VR101 until table increases speed, then turn pot back until table decreases speed and then turn pot to central point of stable speed. Repeat on 78 with VR102. Please advise if you think this is shaky advice...

WATCH OUT for shorted probes. Probe points 0v, S and T are direct connections to the circuitry and are not isolated by resistors or whatever. I had to replace one transistor due to probe shorting (scrap-box again, thank goodness).

Apart from that, and a moment when a badly soldered +5v wire broke off and shorted on the plate, all went well. I went from happiness to despair about 4 times that afternoon.

I carefully oiled and cleaned up the bearings and it works 100%. The Technics label is gone long in the past (anyone know where I can get one?) but the table itself is essentially good.

The second SP10 responded well to a wiser and poorer man and I managed to get it humming, also with new LED strobe, without much difficulty.

So now I have one I use and a spare. Looks like my old Garrard 301 will not be missed so much any more...

Thanks for listening, I appreciate any comments if you think I have missed something.
I either do, or I don't. There is no 'try'.

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