Sp-10Mk2 - Help required

turning japanese
tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Sp-10Mk2 - Help required

Post by tcp » 15 Aug 2012 12:59

Hi, I'm a newbie here and would very much to seek Help from the experts here.

I ran into some problem after I replaced all the electrolytic caps in my SP-10. All cap values are replaced with same value. I started the TT and initially it ran ok apart for 33 1/2 rpm where some noise can be heard (wasn't spinning as smoothly as 45rpm and 78rpm). I immediate turned it off and noticed a burning smell. Unfortunately I couldnt trace the source of the burning smell. Upon further checking, seems I might have shorted IC 15 with some residual solder. Had that IC replaced but now the TT just spins at a constant (fast) speed, switching speed has no effect at all. The strobe does not work as well.

I've done all the maintenance/troubleshooting checks as per the service manual and have narrowed down to the faults possibly in the Control Circuit. I've check P1 (which is also pin 14 of IC 2) and there's no signal/sine wave. Is this an indication that the Quartz is damaged?

I hope some experts out there can Help.

Thanks in advance

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 16 Aug 2012 00:47

Anyone with some knowledge and perhaps experience?

SupaWales
member
member
Wales
Posts: 181
Joined: 03 May 2009 16:52
Location: Port Talbot

Re: Sp-10Mk2 - Help required

Post by SupaWales » 17 Aug 2012 17:05

OK tcp.

I don't know why no-one has responded.

I don't own a SP10 MkII, but do have 40 years experience designing & repairing electronic equipment.

I suggest the following, based on looking at the diagram in the service manual which is available here on VE.. see
https://www.vinylengine.com/library/technics/sp10.shtml
Scroll down for the list of manual download links.

Connect your 'scope to pin 1 of IC2.

Do you see a sine wave?

If not, measure the 5v supply rail that feeds IC2 TR218 / 9 etc.

If there's no 5v supply, check fuse F1 on the power supply board and change if blown
The fuse is 1A fast blow.

There is a possibility if the fuse has blown that there is damage to the 5v supply, so you may want to check TR404, 403, 402 & 401 with a multimeter just in case.
It may also be possible that the rectifier have failed D401, 402.

I would say that it is unlikely that X1, the actual quartz crystal has failed because of the problem you describe.

I don't want to sound like I'm trying to teach you how to "suck eggs", but please watch out for the high voltages on the PSU board and elsewhere.
There is 140v DC from the PSU on the logic board for the strobe neon.


Please chack as above and report back here if you still have problems.

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 18 Aug 2012 04:53

Hello Supawales,

Thank you so much for the reply and tips. Really appreciate it.

Yes I am and have been following the manual as per the link for the past few days and am at a loss.

Pin1 of IC2 (aka P1 in the manual) does have a signal but its very small and nothing like the indicated picture on the diagram (sine wave 0-4v). I measured DC there and its 2v. I've also checked TR218; pins E/C/B measures 1.8v/4.6v/2.6v (vs per specs of 2.2v/4.4v/2.4v). Am wondering if the difference at E (1.8v vs 2.2v) an issue - perhaps too low? I will check the rectifier as per your request.

Once again, really appreciate your response.

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 18 Aug 2012 07:32

Following my earlier reply, I've checked the Connectional Circuit points C1/C2/C4 and they are 152v/5v/32v respectively (specs 140v/5v/32v). This should indicate 5v supply is ok.

The sine wave at pin 1 (IC2) does not look right.

SupaWales
member
member
Wales
Posts: 181
Joined: 03 May 2009 16:52
Location: Port Talbot

Re: Sp-10Mk2 - Help required

Post by SupaWales » 18 Aug 2012 11:48

OK tcp..

Disconnect IC2 pin 1 from the osc and then check the osc output again with 'scope.

If it looks better, replace IC2.

If not better, replace TR219 and check value of R246 ( 820 ohms ).

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 18 Aug 2012 12:56

ok.. I will need to purchase the transistors and IC chips. I will revert once done. Thanks!

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 21 Aug 2012 04:21

R246 checked out OK (819 ohms). Removing pin 1 of IC2 did not improve the sine wave. I will try to find a replacement for TR219.

Trouble is the parts (IC and transistors) are non-existent locally. I will have to try to order from the internet. Do you have any store to recommend?

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 21 Aug 2012 08:11

I managed to track down resistors part 2sc1328T locally. I've since replaced TR218, 219, 201,202,203,204. With pin1 of IC2 disconnected, still not getting a proper sine wave.

SupaWales
member
member
Wales
Posts: 181
Joined: 03 May 2009 16:52
Location: Port Talbot

Re: Sp-10Mk2 - Help required

Post by SupaWales » 21 Aug 2012 16:01

Hi tcp..

More things to try.

Check that the xtal trimmer hasn't gone faulty by removing it and checking the waveform at IC2 P1.
The osc will run without the trimmer happily.
If you can't get a new trimmer cap, try cleaning the old one by rapidly adjusting it a dozen times from end to end of it's travel.
You can substitute it with 2 x 8cm length of thinly insulated wire twisted together.
Adjust freq by twisteing more or less of the 2 lengths of wire together.
Any excess not required can be cut off.

Substitute or replace the crystal 3.5796MHz.
Sub with RF generator 3.5796 @ 4v p-p into IC2 P1 and check turntable function.
3.57xx xtal is easy to find if your TV system is NTSC.. find old CRT TV and check the chroma subcarrier regen..

Put a scope across the 5v supply set to AC coupled 10mV per div and tell me how much ripple, noise etc. there is.

Why have you replaced TR401 - 4? They have nothing to do with the osc or buffer which appears to be where your fault lies.
Personally, I would refit the original devices unless you are certain they are faulty.. measure junctions with diode test on DMM / AMM or gain using transistor hFE function. Faultfinding may become harder by introducing more man made faults...

Earlier on you said the fault was caused by a short around IC15 and that there was smell of burning.
Please describe which pin(s) of IC15 were shorted and what were they shorted to.. each other, some other circuitry or each other and some other part of the circuitry.

If you cannot see any damaged or burnt components, please take high resolution close up pictures of the component sides of the boards and upload somewhere or email me at ( mw0cdo at gmail dot com ) so that I can look..

Did you check all the el-caps you replaced were OK before soldering them in?
Even new "boutique" caps can be faulty.
Are the all in the right way round ( polarity) ?

Finally, have you double checked that you don't still have solder bridges where they shouldn't be?

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 22 Aug 2012 12:21

Re; TR201-4 replacement. I forgot to mention that I'm not getting a nice square wave at pin 1 of IC1. Thats the reason for the replacement.

Seem to have made some progress. I replaced the crystal with a new one - 3.5795MHZ (diff of 0.0001) and also C210/211/214. The TT has now 3 speeds (speed not verified yet) albeit jittery rotation with 33 1/2 being worst and 78 being the smoothest. The strobe light is also permanent on. The square wave at pin1 of IC1 is also looking better although not exactly square yet. It was a right-angle triangle and now it is with a rounded top left corner. As for the osc trimmer, which point do I measure on the board if I need to adjust? Its not mentioned in the manual.

The shorted pins are 3/4 on IC15. Unfortunately I couldn't locate the burnt components by smell nor by sight.

Noted your comments about replacing components blindly. I totally agree with you.

SupaWales
member
member
Wales
Posts: 181
Joined: 03 May 2009 16:52
Location: Port Talbot

Re: Sp-10Mk2 - Help required

Post by SupaWales » 22 Aug 2012 14:22

OK..

The test point for the osc freq 3.5796 is P1 ( also Pin 1 IC2.

You'll need a frequency counter to set the correct frequency.

Osc freq is set using C210 but for the time being the absolute accuracy of 3.5796 is not needed.

Before worrying about square wave shape, double check that your scope probe compensation is adjusted correctly.
Rolled off corners and tilted tops / bottoms can be caused by improperly compensated x10 probes.
Use the square wave gen built into your scope for the purpose and check your probe(s) are correctly compensated before trusting the waveforms you see.
Once the probe is connected and controls set to produce a locked waveform, adjust the trimmer capacitor in the probe for the best possible square wave shaping.
Then take another look at the waveforms in the SP10.

You say that the strobe neon is on permanently which is a bit of a clue.
The 2 transistors which switch the neon ( TR217 / 6 ) are driven by IC15 pins 3 & 6.
Pin 4 of IC15 is directly connected to pin 6 of IC16.. & you say pins 3 & 4 of IC15 were shorted together..
3 things I'd try are removing TR216 & 7 and measuring them for OC / SC junctions.
Replacing IC16
Following the fault finding flow chart sections C & D but unfortunately the manual
ve_technics_sp10mkii_euro_service.pdf has the RH edge of the flow chart missing so a little info is gone.
Can you run through the checks in C & D and report findings?

SupaWales
member
member
Wales
Posts: 181
Joined: 03 May 2009 16:52
Location: Port Talbot

Re: Sp-10Mk2 - Help required

Post by SupaWales » 22 Aug 2012 14:32

Had another look in the library..

Download
https://www.vinylengine.com/ve_download ... ervice.pdf

The fault finding flow charts are complete and the block diagram has more annotations so you should be able to get a better understanding of the exact function of each block of circuitry.

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 22 Aug 2012 15:39

OK. The ordered IC chips should arrive in the next couple of days. Apart for IC 15 (only 3 left in the entire country which I've bought them all). None could be found locally.

The scope has been calibrated etc. All other check points in IC 1 read square waves except pin 1.

I also discovered another anomaly, the wave form on pin1 of IC 10 is abnormal; 3 square waves followed by flat line and then 3 square waves and flat line and so forth. This appears to coincide with the rotation of the motor. I back traced and suspect IC 9 is damaged too as the input signal at pin 1 of IC 9 (aka P2 check pt) has a normal square wave pattern at regular intervals. The output at pin9 (IC 9) leading to pin 1 (IC 10) has the same abnormal signal (same as pin1 of IC 10). In any case, I'll tackle TR216/17 and IC 16 before proceeding elsewhere.

tcp
junior member
junior member
Posts: 15
Joined: 13 Aug 2012 12:48

Re: Sp-10Mk2 - Help required

Post by tcp » 22 Aug 2012 16:02

Sorry, made a mistake, C210 was not replaced, it was C213. I couldn't find a new trimmer cap replacement. Could you please elaborate the substitute of 2 twisting wires - where are the ends connected to etc? am trying to picture it..

Locked