hifi engine

Marantz 2285

Peter's picture

Just curious if anyone knows, what makes the tuner on this Marantz 2285 weak? Sure I can adjust the signal meter so it looks as though it's pulling in the station strong, when in fact it's not? I would like to get this thing tuning like it did when new if possible? Everything else works as it should, with no other problems identified, and the unit is untouched!
Regards
Pete



Marantz 2285

Could be a lot of things, like a bad or damaged antenna or downlead, bad balun at the antenna input, bad FET, poor connections, mis-alignment, bad caps.
One point though: you say you can adjust the signal meter, then you say the unit is untouched. What work have you done on it?

Peter's picture

Marantz 2285

None at all, just tinkered with the adjustments for meters is all, didn't help so I put them back where they originally were. BTW, thanks for the reply

Peter's picture

Marantz 2285

Also, I guess really what I meant stating unit is "untouched" is nothing has been replaced, all original and still kickin' butt! Sorry for any confusion, I didn't realize I didn't explain myself.

Regards
Pete

Marantz 2285

Peter,
I have found that almost all vintage units such as these have "weaker" FM and AM reception than when they were new. I attribute this usually to component values drifting out a bit over many years. All of the resistors and capacitors in the RF, IF and MPX sections have aged, and while they may still be in tolerance, their values may be slightly off from their value when the unit was built, and factory aligned. This can result in non optimal tuning. Dirty bearings on the pivots of the tuning capacitor, and bad ground connections on where the FM front end secures to the main circuit board are other areas that affect signal strength.

When I get an old unit, I typically work on the restoration the following way:
Completely blow out the unit with a compressor.
Do a quick checkout of the unit
If I am getting AM and FM stereo, I usually assume the unit to be functioning
I resolder all ground connections for the FM front end to main ckt board, or tighten screws to chassis.
Using a syringe, I apply a small amount of synthetic oil to all the bearing points on the tuning cap.
(be careful to use a very small amount, and not getting any running onto fins)
Using headphones, I align FM front end be ear and by signal meter according to service manual
(caps for high end of scale, coils for low end). Then adjust oscillator for proper dial indication.
I only adjust the discriminator coil if center tune is off. This can be tricky.
I don't mess with the mpx coil setting unless the separation is very poor.
You need to listen via headphones and monitor the stereo light with any adjustments on the mpx board
I never really adjust the pot for tuning meter level, as the previous tuning usually pulls it in.
While there is a lot of specialized test equipment that is recommended to align FM circuits, I have been very successful with aligning for best signal strength and sound. But you need to make sure that you listen via headphones, and only adjust one item at a time. If you do something that causes the sound to decrease or distort, or the signal level to drop, you need to restore this setting to its previous state, before going onto something else.

But if you aren't familiar with electronics at this component level, I would suggest that you find someone to do it, or help you with it. My comfort in doing this by ear and VU meter is that I have been doing component level stuff on and off since 1969.

Good luck
Tom

Peter's picture

Marantz 2285

Wow! Thank you for taking the time to type all that out, I agree with you totally towards the end of your reply about getting someone else involved. I surely don't want to do anything wrong to this because even though the tuner is being somewhat finicky, it still is tolerable, and still sounds fantastic! I will definately take your advice and seek more experienced personel with getting this thing back to where it should be or where it was once apon a day! Thank you again for the reply.

Regards
Peter