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SL1600mk2 Pitch Control LED Repair

I've just come across this problem with a 1700 Mk2. The pitch control changes speed as it should but the LEDs only light at the green quartz lock position or the far right +6% position.

Before I order ICs and open it up, I wonder if anyone has recent or updated comments on the issue.
 
Hmmm, I don't see stock of CD4011BEE4 at Mouser or Digikey or my other usual sources. Any tips?
 
elnaldo said:
CD4011 are 4-ch, 2-input, 3-V to 18-V NAND gates.

The link you posted opened a CD4096 page, the 4096 is a different part,
"IC CMOS CD4069UBE - HEX INVERTER"

You need a 4011 in some of their variants
https://leeselectronic.com/en/product/7193-7193ICCMOS4011QUADNANDGATE2IPDIP.html
(Check also HCF4011 )
Click to expand...

Thanks. That's helpful. The 4096 was just what the search on Lee's returned; I didn't plan on using it. I can order online from Mouser but I go to Lee's store often enough as they are very local so thought I would check.
 
@Montycat, did you solve your problem? I'm waiting for ICs from Mouser for my 1600 Mk ll.

Also, have a flaky Auto Start. I've gone in 3 or 4 times trying to figure out what the problem is (suspect the record size LEDs/sensor) but haven't found a smoking gun. Every time I put the table together again and hook it up, Auto Start is back. I play it for awhile and it goes away again! The deck is messin' with me!!

When I opened it up today, I replaced the 10uf/16V tantalum cap with an electrolytic, cleaned all the male plugs with D5, and tested diodes on the Tonearm Drive Board (all good). Put it back together and it's working fine... so far.
 
JJCalvillo said:
@Montycat, did you solve your problem? I'm waiting for ICs from Mouser for my 1600 Mk ll.

Also, have a flaky Auto Start. I've gone in 3 or 4 times trying to figure out what the problem is (suspect the record size LEDs/sensor) but haven't found a smoking gun. Every time I put the table together again and hook it up, Auto Start is back. I play it for awhile and it goes away again! The deck is messin' with me!!

When I opened it up today, I replaced the 10uf/16V tantalum cap with an electrolytic, cleaned all the male plugs with D5, and tested diodes on the Tonearm Drive Board (all good). Put it back together and it's working fine... so far.
Click to expand...

No, not yet. I am in no rush either as it's completely functional, save for a few LEDs, plus I have lots of turntable options. I might drop into the local store soon to pick up the IC though.

I'm watching your progress with interest though. I wish I could help more.
 
Montycat said:
No, not yet. I am in no rush either as it's completely functional, save for a few LEDs, plus I have lots of turntable options. I might drop into the local store soon to pick up the IC though.

I'm watching your progress with interest though. I wish I could help more.
Click to expand...

It's more amusing than anything. I've got good backups too, so no hardship. Just wanna show this deck who is boss!
 
Hello. Time to take the schematic and study the circuit. I think you need to check the signals with an oscilloscope, perhaps a multimeter is enough. All those ICs are logic switches, they output a high or low voltage depending of the voltages at the input pins. A bad IC will have wrong voltages, not according to the logical table explained in the datasheets.

So, now you have a working TT, at the right speed, but the pitch is not working.

does it go to a fixed speed, or do you have some speed changes when you move the pitch control? Have you checked the pitch potentiometer itself? It could be broken, or installed in a wrong way.

Have you read the service bulletin referring to Auto Start problems?

sl1600-problem.png
 
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elnaldo said:
Hello. Time to take the schematic and study the circuit. I think you need to check the signals with an oscilloscope, perhaps a multimeter is enough. All those ICs are logic switches, they output a high or low voltage depending of the voltages at the input pins. A bad IC will have wrong voltages, not according to the logical table explained in the datasheets.

So, now you have a working TT, at the right speed, but the pitch is not working.

does it go to a fixed speed, or do you have some speed changes when you move the pitch control?

Have you read the service bulletin referring to Auto Start problems?

View attachment 2348809
Click to expand...

Fully functional except for the LEDs when pitch is adjusted off 33.3 or 45 rpm. Pitch control works to some degree, it speeds up and slows down, not sure exactly how much. Whether I speed it up or slow it down, the LEDs goes directly to -6%.

Saw the bulletin but don't have those symptoms.

Trouble-shooting in the service manual has a notation for "Pitch Control Malfunction", #4, but the actual pitch control seems to be working. There's also one for "LED Not Illuminating", #5, They illuminate they're just not accurate. I'll look at those, but not sure if either is exactly what's happening.
 
JJCalvillo said:
Fully functional except for the LEDs when pitch is adjusted off 33.3 or 45 rpm. Pitch control works to some degree, it speeds up and slows down, not sure exactly how much. Whether I speed it up or slow it down, the LEDs goes directly to -6%.

Saw the bulletin but don't have those symptoms.

Trouble-shooting in the service manual has a notation for "Pitch Control Malfunction", #4, but the actual pitch control seems to be working. There's also one for "LED Not Illuminating", #5, They illuminate they're just not accurate. I'll look at those, but not sure if either is exactly what's happening.
Click to expand...

There is an adjustment for the pitch leds, VR425. I'd check if adjusting that makes a difference, or check the circuit around that adjustment. It's connected to IC428 and IC429. I'd check voltages on those 2 ICs to see if you find some anomaly.
 
VR425 doesn't move the LEDs. Checked the VR and it measured .7 - 407 ohms. Moves smoothly through the range. Listed to be 500 ohms.
Starting to test points in the neighborhood.
 
Latest is the table continues to work the way it should, though the LEDs are only correct when the pitch control is centered and the Green LED is lit.

Pitch control will will adjust speed correctly according to the strobe/platter, but the LED is either green or -6%. So far I've:

• Replaced IC426/427 on the control board, nothing changed.

• Put the scope on to do the A/B adjustment on pg. 7 of the SM and got a good wave for both but trying to adjust VR425 to get the +3% LED to light didn't do anything, the LED stayed lit at -6%.
A
ScopePartA.JPG

B
ScopePartB.JPG

• Went to TP8 and got a flat line, not the wave.

• Went to TP12 on the Drive Board and that was flat as well, unless I move the pitch off center, then roll it to center and past. Then I get one spike when it hits center, and another spike when it goes off center.
ScopeTP12Adjust.JPG

Not sure where to check next?
 
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Because it's not a problem that keeps me from using the table, I haven't searched any farther. I will when it's time to give my Dual 721 some play.

I replaced ICs 426 and 427, but I'm guessing one of the ICs on the Drive Board is bad. IC 302 is the same one as IC 427 and I have an extra, so I may try that first and if it doesn't help, I'll start measuring other ICs.
 
DOH!

Went to play my new Kinks "Word of Mouth" in translucent red vinyl and auto start (AS) wouldn't work for the first time in forever. Think to myself I have to fix the speed LEDs anyway, I'll just tighten up the contacts to the Drive Board and record size LEDs while I'm in there (the AS problem last time).

Set up the backup table and hit start and realize I'm an idiot, the 1600 ll was working exactly as it was supposed to. It was reading the signal through the translucent record and thinking there was no record on the table, so it shut down the AS.

Will give the Dual 721 some days of action, and see if I can get the speed LEDs working on the 1600 ll.
 
hatman said:
Technics SL1600mk2 - Control Board /LED Pitch Control problem

Problem with 'Pitch Control' LEDs (total 12 Red & 1 Green);
Center Green LED works, as does control of motor/ platter speed via Pitch Control. When control is moved to any + or – position, the green LED goes out as expected, and the far right (red) LED goes on.

Repair 6/20/12: Replaced IC427, (TD4011BP Toshiba) with CD4011BEE4 (Texas Instruments) from Mouser Elec. @ .50¢ (14 pin PDIP, through hole).

PM me if you want detailed info on this repair or my other post today regarding small gear replacement on the SL1600mk2.
Click to expand...


I replaced IC427; it did not fix the problem. It isn't any worse, just not fixed.
 
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