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I realize this is an old thread, but I thought I would post this anyway in case someone else comes across this problem. The cause of the low level hum is not the main filters. It is caused by the 4, 10uF 25v surface mount capacitors near the regulator ICs. (I hate surface mount caps!)

Look into "Mu metal shielding"

Maybe a Rolling Rock?

Thought I would post this in case someone else has run into this problem. Customer brought in this amp which had been in another shop. Came with a bag-o-parts, of which only 2 output transistors were bad. The problem was that the right channel would bias correctly, left channel would not (low...

I seem to recall moving the regulator transistors and mounting them to the chassis in a unit (could have been a Pioneer) years ago. Requires insulator pads etc. Somewhat of a pain, but it solved the problem.

I just finished servicing a 1900. These units have plug in circuit boards, one of the driver board connectors was intermittent. I suggest removing and cleaning these (all) boards and connectors.

Sorry it took so long to respond. Been having computer problems. What can I do for you?

The upper spindle motor bearing needs lubricated. Very hard to get to. I had to use a small tube (I mean SMALL) to get the oil to the motor shaft. Also, check the clamper bearing plate and see if it has a divot worn in it where the bearing rides. Good luck.

Just a drop of oil on the shaft where it comes out of the motor. Do not try to remove the disc table. Good luck

Be sure to lubricate the upper spindle motor bearing. Very common cause of erratic skipping.

Donald Fagan, The Nightfly

I am located in southern Idaho. Have done Marantz for 40 years. Be glad to help.

A good customer of mine and fellow AK-er sent me a sweet little Optonica SM-3636 integrated amp for repair. Unfortunately, the right channel output pack was shorted. after looking all over the inter-web, the RH-iX1055af pack (made by Sharp) was nowhere to be found. Things were a little slow...

Great thread! Great memories! I worked for Pacific Stereo in their service departments for years. Started in the Seattle region, worked in just about every store including the big one in the University district (I think there was a Peaches Records next to it). Transferred to the bay area where I...

I agree with dlucy. The schematic shows 2sd600/2sb631. The ones in my unit may have been changed at some time.

The original # is 2sd669a. I have one of these receivers in the shop. I used to work for Pacific Stereo, and was the service manager at the Bellevue store, and several others in the Seattle area during the late '70s. The Reference 450r is indeed the same output/driver stages as the Concept 4.5...

Yes, just the electrolytics. Note; NTE 703/703a is a direct sub for the ua703. Good luck

If it's constructed like the 800, the I.F.-mpx. board is a bear to get off. If you haven't already done so, plan on re-capping this board. Make good notes, drawings, pictures etc. so you know where every wire goes. You will have to cut the ground connections and re-do them when you put it back...

The 250 TX has a Varactor FM front and and a normal AM front end. The tuning capacitor you see is only for AM. The FM tuning is done by varying the tuning voltage to the FM front end, using the potentiometer on the back of the AM tuning capacitor assy. or the tone-o-matic controls. This voltage...

Highly recommend Radiodaze.

The most likely cause is there is a short after R224. Take a resistance reading from both sides of R224 to ground.

If c208 or c209 are shorted (look below h203 on schematic), it would kill the voltage on those transistors, but not on the others, due to the 47 ohm resistor in the line. It would probably drop the 13.4 volts line down also. Just a thought. Good luck

Unless you have records which were encoded with the CBS SQ system, and a cartridge meant for the same, the decoder is fairly useless.

Yes, the equipment under the bench is Sencore, TVA92 and VG91 from when I used to work on CRT Tvs. Fortunately, don't see them much any more except for an occasional arcade game. As for the patch panel, they were made by Pacific Stereo, not sure which came first. I agree that the Sencore PR 57...