[Gary Blake]

Hello, new to the forum and looking for some help.

I have a complete Harman Kardon system purchased new in 1983. Consists of a PM660 amp, CD401 tape deck, TU615 tuner and T60 turntable. Hooked up to a primary pair of Merak M4 speakers and Bose 301’s secondary.

The system has been sitting unused for about 20 years (3 children and life got in the way).

Now trying to get the system up and running again. Would classify myself as very handy but electronically challenged.

So far have re-foamed the M4’s – 2 woofers and 4 passive radiators.

Done a complete re-cap on the PM660, replaced trim pots and re-set bias current and DC offset. (Was suffering from left channel problems and high DC offset) Back up to full power again both channels, DC offset within limits and stable, minor problem with tape out switch left to fix – so all is good here and the Meraks sound great with the new foams.

I am currently trying to resurrect my Harman Kardon T60 turntable. Time has not been kind, motor is none functioning and transformer has now quit. Have located a replacement motor. Now looks like I need a new power supply. Original was suffering from low output and is now totally dead.

The original HK part number is 5584-701411
The original transformer is marked TKK looks like their part number is TKP0104-A36. (Also marked on the transformer by the TKK logo is 12 2L3.

It would appear the output voltage is supposed to be 14v according to the schematic in the service manual. Can't find anything in the schematic to indicate output current.

Can anyone help with the output current specs or source of supply for a replacement?

While waiting for parts I have replaced all the capacitors, motor switch, and fixed a couple of bad solder joints on VR101 and VR102 trim pots.

Have read about the Van Alstine outboard power supply modification and was also planning to do this modification after I got the table running again. With the death of the transformer I may have to do the outboard power supply first.

Just wondering if anyone has done this modification and replaced the original transformer?

Google has not returned any results for locating an original part and 14v transformers do not seem to exist any longer.

I have been told that a 12v transformer will work in an outboard power supply and also that the current spec is not critical in an outboard power supply.
Any assistance in this would be greatly appreciated.

Gary

[Gary Blake]

Update:

Got the new transformer (115v @ 60hz input 14v @ 28Va).

Built the new outboard power supply according to the Van Alstine plans. (The only difference being the switch with built in LED)

The new transformer unfortunately is putting out 16 volts instead of 14, and at the output of the outboard power supply is about 21 volts (after the bridge diode). According to the Van Alstine plans with an original transformer the reading here should be about 15 volts.

Not sure what to do here next, worried the 21 volts may be too high.

Also wondering if the 115v rating of the transformer is affected by my local current which is running between 119 and 121 volts. Is this is what is causing it to put out 16v instead of 14v. I thought 115 and 120 were interchangeable based on slight variances in local power supplies.





Gary

[avahifi]

There is a pretty simple fix.  Just add a 12V regulator to the output of the power supply.  A LM7812 should work fine.  You connect the raw DC to the input terminal, the ground terminal to chassis ground, and the output terminal will supply you with +12DC.  Add a .33uf 63V film capacitor to ground close to the input terminal and a 1 uf 63V film cap to ground from the output terminal.   Follow that with a 1000uF 16V lytic to ground and you are set to go.

You may need to add a heat fin to the 7812 depending upon the voltage in and current draw.  If it is staying below 120 degrees F you are ok without the heat fin.

Whoops, what are you using to convert the 14V AC from the power transformer to DC?  The HK motor runs from DC, not AC.  This requires a diode bridge and a few more parts that were built into the original HK power supply board that we used for this purpose, simply moving it to the external power supply box.  Did you overlook the need for the diode bridge?  Note that 14V AC will yield about 20V DC after a diode bridge.  Then you would need to regulate that down to 12V DC as mentioned above.

Frank Van Alstine

[WGH]

How many amps does the motor need? A used Acopian 12v DC linear regulated power supply can be found on eBay for $13-$65.

[Gary Blake]

There is a pretty simple fix.  Just add a 12V regulator to the output of the power supply.  A LM7812 should work fine.  You connect the raw DC to the input terminal, the ground terminal to chassis ground, and the output terminal will supply you with +12DC.  Add a .33uf 63V film capacitor to ground close to the input terminal and a 1 uf 63V film cap to ground from the output terminal.   Follow that with a 1000uF 16V lytic to ground and you are set to go.

You may need to add a heat fin to the 7812 depending upon the voltage in and current draw.  If it is staying below 120 degrees F you are ok without the heat fin.

Whoops, what are you using to convert the 14V AC from the power transformer to DC?  The HK motor runs from DC, not AC.  This requires a diode bridge and a few more parts that were built into the original HK power supply board that we used for this purpose, simply moving it to the external power supply box.  Did you overlook the need for the diode bridge?  Note that 14V AC will yield about 20V DC after a diode bridge.  Then you would need to regulate that down to 12V DC as mentioned above.

Frank Van Alstine

I think I have my answer - I was measuring the DC voltage with just the power run in to the box without the turntable hooked up - apparently this is not a valid measurement, the outboard needs  to be hooked up and under load in order to show the actual DC voltage in use. Another HK user who has done the same mod has advised he has the same readings as mine with no load, under load they are where they need to be at about 15 volts.

The diode bridge is in place - plans were taken directly from your 1985 Audio Basics article.

Thanks for the reply and the original article and plans.

Gary

[WGH]

I did the mod years ago on my T55C, no load DC voltage is 17.8 V with original transformer and diode bridge.

[Gary Blake]

I did the mod years ago on my T55C, no load DC voltage is 17.8 V with original transformer and diode bridge.

Thanks for the reply - I saw your post on the T55c mod - one of the ones I read that convinced me to try this modification. Looks like the T55C has a different TKK part number for the transformer so the output may be slightly different. Another T60 user with the modification is reporting 20.5volts no load so I guess I am in the right range. As soon as I finish some other repairs to my T60 I will hook it up and retest under load just to make sure.

Gary

[blackterra]

Hi Gary,

I realize this is a pretty old thread but I'm wondering if your outboard transformer fix worked. I would like to do the same. My original t60 transformer is outputting only 9 volts. The motor is not working. At this point I'm not sure whats wrong. If you got your new transformer to work then I could try it as its a cheap test.
I would appreciate any input you might have on this subject.

Mike