Technics CD-4 Cartridges with no audio output

[RetroQuad]

My question regards 2x Technics CD-4 cartridges I have that won’t produce any sound. Both have their original Technics Shibata stylii (still in great condition) and I also tried a brand new aftermarket stereo only stylus, but still no audio output. I tried a regular stereo cartridge in the same head shell on my Technics SL-Q2 and that worked fine, confirming the turntable and amp are fine.

I used my multimeter to test the cartridge, as recommended by Shure on this web page - https://service.shure.com/s/article/testing-a-phono-cartridge-body
I also tested 3 other cartridges I have, and the results I got for the Left and Right channels were as follows -

Technics EPC-460C - 910 ohms (L) 956 ohms (R) ... (No audio output)
Technics EPC-451C - 787 ohms (L) 767 ohms (R) ... (No audio output)
Grado FT+ - 674 ohms (L) 672 ohms (R) ... (This cartridge works well)
Shure M95ED - 1467 ohms (L) 1477 ohms (R) ... (This cartridge works well)
Shure M75-6S - open circuit ... (This cartridge is known to be faulty and will not work)

As mentioned in the Shure web article "If you get similar results to the numbers listed above, the cartridge is OK and the problem lies after the cartridge output" ... BUT this is NOT correct for my 2x Technics CD-4 Cartridges. After not producing any sound (thru my amp and speakers) I used the cueing lever to lift the EPC-460C cartridge up, and then I used a small metal screwdriver to touch the left (white) contact on the back of the cartridge and heard a loud buzz through my left speaker. Then I touched the right (red) contact and heard a loud buzz through my right speaker. So there is no problem “after the cartridge output”.

So why won’t my 2x Technics CD-4 cartridges produce any sound when playing a record? The EPC-451C came new in a Technics SS-2900D floor system, purchased here in Australia about 40 years ago, and after being in storage for the last 25 years, the cartridge no longer produces sound. The EPC-460C was purchased recently from Japan as a replacement, but it doesn't produce sound either. It seems like a big coincidence that they both exhibit the same symptoms. Does anyone out there have a similar Technics CD-4 cartridge, and is it still working fine? or does anyone have a faulty one like mine? What is there that could be wrong with both these CD-4 cartridges? and very importantly is it fixable?

 

[Beefalo]

My question regards 2x Technics CD-4 cartridges I have that won’t produce any sound. Both have their original Technics Shibata stylii (still in great condition) and I also tried a brand new aftermarket stereo only stylus, but still no audio output. I tried a regular stereo cartridge in the same head shell on my Technics SL-Q2 and that worked fine, confirming the turntable and amp are fine.

I used my multimeter to test the cartridge, as recommended by Shure on this web page - https://service.shure.com/s/article/testing-a-phono-cartridge-body
I also tested 3 other cartridges I have, and the results I got for the Left and Right channels were as follows -

Technics EPC-460C - 910 ohms (L) 956 ohms (R) ... (No audio output)
Technics EPC-451C - 787 ohms (L) 767 ohms (R) ... (No audio output)
Grado FT+ - 674 ohms (L) 672 ohms (R) ... (This cartridge works well)
Shure M95ED - 1467 ohms (L) 1477 ohms (R) ... (This cartridge works well)
Shure M75-6S - open circuit ... (This cartridge is known to be faulty and will not work)

As mentioned in the Shure web article "If you get similar results to the numbers listed above, the cartridge is OK and the problem lies after the cartridge output" ... BUT this is NOT correct for my 2x Technics CD-4 Cartridges. After not producing any sound (thru my amp and speakers) I used the cueing lever to lift the EPC-460C cartridge up, and then I used a small metal screwdriver to touch the left (white) contact on the back of the cartridge and heard a loud buzz through my left speaker. Then I touched the right (red) contact and heard a loud buzz through my right speaker. So there is no problem “after the cartridge output”.

So why won’t my 2x Technics CD-4 cartridges produce any sound when playing a record? The EPC-451C came new in a Technics SS-2900D floor system, purchased here in Australia about 40 years ago, and after being in storage for the last 25 years, the cartridge no longer produces sound. The EPC-460C was purchased recently from Japan as a replacement, but it doesn't produce sound either. It seems like a big coincidence that they both exhibit the same symptoms. Does anyone out there have a similar Technics CD-4 cartridge, and is it still working fine? or does anyone have a faulty one like mine? What is there that could be wrong with both these CD-4 cartridges? and very importantly is it fixable?

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Hello @RetroQuad
Welcome to the QQ forum !

 

[Circular Vibes]

If you can use other cartridges and not the Technics, that means you are not switched to strain gauge preamp. Those cartridges require a voltage be applied to them to work. I don't know your system to comment of there is a switch on back.

 

[RetroQuad]

If you can use other cartridges and not the Technics, that means you are not switched to strain gauge preamp. Those cartridges require a voltage be applied to them to work. I don't know your system to comment of there is a switch on back.

Thank you for that valuable insight ... I think you may have hit the nail on the head!!

I've worked in hi-fi retail from 1970 and have sold many Technics and JVC CD-4 systems, and even been part of several invited dealer tours to both manufacturer's factories in Japan in the late 70s and early 80s, but have never come across any reference to strain gauge cartridges. I've just done some reading on the internet now and it seems these Technics cartridges do require a small voltage applied to them in the form of a bias current, and that could be the cause of my problems.

The EPC-451C came fitted in a Technics floor system, the SS-2900D, and I guess the inbuilt preamp is no longer applying the needed bias current. I mounted a regular stereo cartridge in this floor system and it produced sound as normal (stereo only of course) so the preamp must still be working, but not supplying the much needed bias current. I'll have to investigate and hopefully be able to fix it.

I also tested both Technics cartridges on my Technics component system using an SL-Q2 turntable, both with and without my JVC 4DD-5 demodulator. My JVC 4MD-10X CD-4 cartridge seems to work fine both with and without the demodulator, so it must not be a strain gauge cartridge like the Panasonic.

One question ... can the applied bias current be harmful to a regular cartridge that is not a strain gauge cartridge?

 

[Circular Vibes]

Do not use a MM cart with the SG setting, it is said to be disastrous. Pull out the back of your cabinet system and look for a push button marked SG/MM. I don't recommend using the strain gauge carts on the other Technics table as the applied voltage will push big pops every time your arm cues a record or returns. I use a fully manual SL1200 for the SG carts. My SL5200 uses a MM cart for that reason.

 

[Circular Vibes]

I found a pic with a Google search that shows the back of your system and the phono input seems to be internal so maybe the switch is too.

 

[RetroQuad]

I found a pic with a Google search that shows the back of your system and the phono input seems to be internal so maybe the switch is too.

The main boards were easy to get at after removing the turntable. There's a small removable phono pre amp board next to the huge CD-4 board, and down on the main board there's a marked off "phase inverter" section. But there is no SG/MM switch anywhere, probably because this is a complete system, and not designed for any different components.

I have the operation manual, but after searching long and hard on the web, I can't find a service manual, and there's no obvious loose or broken connections on the main boards, so I have no idea where the fault could be if the bias current is not being fed to the cartridge. Do you think it could be something as simple as the pre amp capacitors leaking from old age?

I found the service manuals for the Technics SE-400 and Panasonic SE-405 demodulators, which apparently are designed for strain gauge cartridges as covered here ... 4 Channel Cartridge 4CH 450C-II- Vinyl Engine
But I don't have the knowledge to compare either of these demodulator circuits to what is inside the SS-2900D system, and I don't even know if the problem will be in the pre amp board, the phase inverter section, or the CD-4 demodulator board, or elsewhere. Do you think it could be something as simple as a capacitor that has leaked from old age? I think I've got my work cut out for me.

 

[MidiMagic]

The warranty expired?

Have you checked to determine if the pinout on the cartridge was correctly followed?

This strain gage arrangement seems to be similar to mics that need phantom power. They are electret (capacitor) mics.

I worked extensively with strain gages in laboratories, but most of them require at least 3 terminals per sensor. The best ones need 4.

The power needed for strain gages can magnetize the coils in a dynamic pickup.

One other possibility is that the cartridges are moving coil instead of moving magnet. They need different preamps.

 

[RetroQuad]

Success at last!! Woohoo!!

While I had the circuitry exposed I removed and reconnected every plug-in cable connector and generally made sure everything was clean and tight. I then re-assembled everything and tested, and now my Technics CD-4 cartridges are working well. Obviously sitting in storage for so long resulted in a bad connection somewhere in the SS-2900D.

I've just been listening to a few tracks from my Doors and Rick Wakeman CD-4 records. I've got Pink Floyd's Dark Side Of The Moon quad album too, but it's only an SQ release, so nowhere near the channel separation. I wish that one had come out in CD-4.

 

[Wurly1]

Hi! Happy to know you fixed it. I have a SS-1100D CD-4 system and under the turntable there is a small pcboard for adjusting the DC bias of the EPC-451C If yours have it you should see holes under the platter to adjust it without disassembling the unit. It must be adjusted only if you replace the GS cartridge. Normally you dont need to touch these. Since there is no schematics availlable, i'm curently retro-ingeneering the main amplifier PC board and part of the input selector, matrix and CD-4 modes selector. Mine have a channel not working and i narrowed the problem to a LD3120 amplifier IC similar to the ones on your preamp pcb. I do not intend to retro-ingeneer the CD-4 demodulator for now but it looks very similar to yours.
Did you find a schematic for it?

 

[RetroQuad]

Hi! Happy to know you fixed it. I have a SS-1100D CD-4 system and under the turntable there is a small pcboard for adjusting the DC bias of the EPC-451C If yours have it you should see holes under the platter to adjust it without disassembling the unit. It must be adjusted only if you replace the GS cartridge. Normally you dont need to touch these. Since there is no schematics availlable, i'm curently retro-ingeneering the main amplifier PC board and part of the input selector, matrix and CD-4 modes selector. Mine have a channel not working and i narrowed the problem to a LD3120 amplifier IC similar to the ones on your preamp pcb. I do not intend to retro-ingeneer the CD-4 demodulator for now but it looks very similar to yours.
Did you find a schematic for it?
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HI, and thanks for your feedback.

I think the SS-1100D is pretty much the same as the SS-2900D without some of the fancy trimmings like the timber look speaker grills, the 4 channel balance joystick and the auto repeat turntable.

Yes, the same small PC board is under my turntable too, and I haven't changed the settings because everything else seems to work fine now. You seem to have a second smaller board with a capacitor on it nearby, that mine doesn't have. Although mine has a strange black probe extending from the screw that holds the end of the board down, just near the green earth connection. It's a piece of springy flat metal covered in black plastic, something like a small antenna. I have no idea what it is for. Your CD-4 board is quite similar to mine, although the layout and components used are slightly different.

Initially the front right channel in my SS-2900D wasn't producing sound, but it was just a very bad volume control pot, and after lots of wiggling I found a few positions where it worked as normal. I won't be able to fix it easily by taking off the volume knob and spraying some pot cleaner, because there are 4 individual pots one behind the other, and the same goes for the bass and treble controls too. I added a photo of this and also the joystick controller front and back to show it's ingenious design. It's quite fun to use too, and I have a wired remote from a JVC amplifier, but it has a different connector, 8 pins instead of 5 because of the addition of a volume control. I'm going to try and find the matching plug and socket and make up an adaptor lead so I can use it on the Technics as well.

It seems you've got your work cut out to fix that amplifier. If only it was a simple dry joint somewhere like in mine. I looked long and hard to find the service manual or even just a schematic, but I had no luck at all. You could always go straight to the top and try sending a request to Technics in Japan.

 

[Wurly1]

Hi thank you for all the informations you provide.

They look the same on the outside but the internal layout is quite diferent. The SS-2900 look neater.
For instance, on the SS-1100D the Bass and Treeble controls work only on the front channels, the back channels are flat which is unfortunate. There is a plug on the back for an external 4 ch balancer like the one built in the SS-2900, i have a similar 4 pot joystick like control that I could use for this. The problem is to find a compatible plug. You have the same problem to solve with your JCV control. The difference on my turntable is this little terminal strip with a filter capacitor to stabilize the dc bias. I think you have one that serve the same purpose but located on the small preamp board instead. Not sure about this but one channel seems to be positively biased and the other negatively.
These amplifiers are very complicated to dismantle to get access to critical parts. The pcbs are overlaping with very little clearance and a lot of cables running from one pcb to the other... It's only after removing the dial light reflector assembly that i found a peculiar fix done by someone else to feed part of the signal from left to right as the right preamp was dead. Some fixing! I put a picture to show you the tiny wire wrapped around two terminals on one of the matrix seIector switches. I already replaced all electrolytic capacitors in the Power supply, Power amplifier and tone amplifier pcb. I also draw the complete schematics of that board. (the pic shown is before capacitor replacement) Next will be the pre-amp and matrix section which look a tad complex. I suspect part of the sound pass thru the CD-4 decoder board even when not using CD-4 decoding. I think you found something like that too... Are the outputs of the SS-2900 amplifiers AN-272 ICs? I love the modular design of the 4 output amplifier boards. Easy to fix and replace, providing new modules are available. lol

See how the pcbs overlap...

Try to locate the tiny wire...

This is the pcb i did the schematics of

On this pcb, IC 402 is dead fortunately i have a replacement available in the mic/guit preamp section.
A real mess... so many wires... lol
I will draw the schematics of the top and left side of the dotted line on this pcb.
That's where the matrix secrets are... lol
No need to do the AM/FM tuner section do.

 

[gvl_guy]

View attachment 53623

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That is the coolest balance control.......and with a remote!

 

[Wurly1]

i have a similar 4 pot joystick like control that I could use for this. The problem is to find a compatible plug. You have the same problem to solve with your JCV control.

I meant 2 pot joystick and JVC control.

 

[RetroQuad]

I meant 2 pot joystick and JVC control.

I found a very similar model Technics receiver that may have the same or similar circuit layout to your SS-1100D, and there's a brochure and manual to download but unfortunately no schematics, although you might be able to hunt one down ...
https://www.hifiengine.com/manual_library/technics/ss-7700.shtml
That's a crazy shortcut "repair" someone did shorting out the pins on one of the matrix switches. It's lucky you can relocate the IC 402 from the mic pre amp. Too bad there aren't some extra AN-272 ICs available there too. Mine has an AN-264 IC but I couldn't see any AN-272s. I've added a few more photos of my SS-2900D internals.

They might have used 4 pots each for the bass and treble controls on the SS-2900D but I can't boost the bass to the small rear speakers separately without also boosting the bass to the large front speakers. I suppose I shouldn't complain though because at least the bass can be adjusted in the rear unlike on the SS-1100D.

 

[Wurly1]

Wow Thank you for the link, it must have been recently added because i checked last month and they had nothing about it.
I've been searching for this model too because of the similarities of the SS-7700 but could not find much info about it.
What i know is the SS-7700 have a quadraphonic output for the mic/guit/mix output and the SS-1100D has only front outputs. (The pcb in the SS-1100D has provision for the additional parts so technically i could add the missing rear outputs.)

The SS-7700 is for 240v 50hz operation (AU) while the SS-7700CU is for 100v 50hz operation (japan).

Thank you for the detailed pictures of your SS-2900 system, it use double sided pcb, making it more compact and less wires. I believe the amplifier is more powerful too.
Definitely a better design!

There is another model very similar to the SS-1100D . The SC-8400DX, it's almost identical to the SS-1100D except it's power supply is designed to operate on 100V 50hz instead of 240v 50hz. You must have noticed the turntable on your model work on 100v, that voltage is provided by a tap on the main power transformer primary winding. I couldn't find any schematics of this model either.
Beside all i told you, i could not find anything else on the web. The rest i learned from drawing the schematics of my SS-1100D.

Another problem i have to solve is the speed of the turntable because in canada we have 120v 60hz
the speed is about 20% too fast. I have a 240v step-up transformer for the system but the motor sync on the 60 hz. These systems were not sold in america so not design for 60hz operation.
I'm looking for a different plater/pulley combination to get the speed right.

SC-8400DX pictures found on the web.

SC-8400DX

SS-1100D (before restoration)

on my 240v system we can see the label on the motor that show 100v 50hz.

Mine has an AN-264 IC but I couldn't see any AN-272s. I've added a few more photos of my SS-2900D internals.

The AN-272 are not visible because they are located under aluminium heat dissipators. The small ic that's not working on my machine (ic402) is a SANYO LD3120 ic (it's intriguing to see SANYO parts in a National Panasonic Technics system specially in early 70's)

 

[MidiMagic]

With most turntables with AC motors, the line frequency determines the speed. The motor synchronizes to the line frequency.

Usually when a turntable was sold to countries with different power, either the correct motor is provided for the power, or a kit with different motor shaft couplings needed by the other power is provided. The diameters of the parts contacting the idler wheel or the drive belt are designed to match the power frequency used.

Wrong voltages usually cause the motor to fail to run, run badly, or burn up. The following voltage/frequency combinations are found:

120V 60Hz - Most of North America, southern Japan
100V 50Hz - Northern Japan
240V 25Hz - Parts of Australia
240V 50Hz - Most of the rest of the world

After burning out the motors on an air cleaner and the two replacements Sears sent me, I discovered the motors were 100V 50Hz intended for northern Japan.

 

[LuvMyQuad]

With most turntables with AC motors, the line frequency determines the speed. The motor synchronizes to the line frequency.

Usually when a turntable was sold to countries with different power, either the correct motor is provided for the power, or a kit with different motor shaft couplings needed by the other power is provided. The diameters of the parts contacting the idler wheel or the drive belt are designed to match the power frequency used.

Wrong voltages usually cause the motor to fail to run, run badly, or burn up. The following voltage/frequency combinations are found:

120V 60Hz - Most of North America, southern Japan
100V 50Hz - Northern Japan
240V 25Hz - Parts of Australia
240V 50Hz - Most of the rest of the world

After burning out the motors on an air cleaner and the two replacements Sears sent me, I discovered the motors were 100V 50Hz intended for northern Japan.

I never realized Japan had two power standards... also, can you see incandescent lights flicker at 25Hz in Australia?

 

[Wurly1]

Wrong voltages usually cause the motor to fail to run, run badly, or burn up. The following voltage/frequency combinations are found:

120V 60Hz - Most of North America, southern Japan
100V 50Hz - Northern Japan
240V 25Hz - Parts of Australia
240V 50Hz - Most of the rest of the world


After burning out the motors on an air cleaner and the two replacements Sears sent me, I discovered the motors were 100V 50Hz intended for northern Japan.
[/QUOTE]

I wonder why they still have 2 different voltage standards in Japan?
I believe it was also the case in early fifties in northern part of Quebec
known as Abitibi, the voltage frequency was 50hz.
They decided to replace peoples appliances for new ones and
changed to the standardized 220 /120v 60hz

In AU the're must be some very annoying light flickering with 25hz.

Strange Sears sent you the wrong motor, at least you found out before throwing it out.

 

[RetroQuad]

The following voltage/frequency combinations are found:
120V 60Hz - Most of North America, southern Japan
100V 50Hz - Northern Japan
240V 25Hz - Parts of Australia ***
240V 50Hz - Most of the rest of the world

*** CORRECTION ... All of Australia is 50Hz for AC Power.

I just checked the internet now to confirm this and the only reference I could come up with was that a suburban electric rail system built in Melbourne in 1918 was served by it's own 25Hz power supply.