[thirtiesradio]

Hi all. I'm not good with solid state items but I know several of you have great knowledge working on them.

I recently picked up a Marantz 2220B receiver that I'd like to use in my shop. It worked but had slight distortion when the volume was turned up. I decided to recap the unit and ordered all the caps. I ended up replacing all capacitors and the unit has much more power now but still has the distortion when turned up. The service manual mentioned setting the power supply voltage on 2 pins to 35VDC (at idle) by turning a pot on the supply board. I'm using a VTVM as they mentioned but I'm only getting just under 20 volts when the pot is maxed. At 20 volts the distortion is much better but I'm wondering what to look at next? Should I disconnect the load and measure the voltage?

[morzh]

Can you put the link to sch if it exist?

Is 35V the output amp's power or one of the preamps?

It is strange they regulate the main power if this is what it is, usually it is simple rectified filtered unregulated voltage.

20V if the 35V is intended, could limit the output and result in clipping distortion at large volume.

[thirtiesradio]

Hi Mike,
The 35V is applied to the main amplifier. Here is a link to the schematic. If the link doesn't work I can try to scan and post it.
Thanks for the help!

http://akdatabase.org/AKview/displayimag...m=1&pos=43

[morzh]

Yes. But there are no pots or regulation for the main voltage. It is rectified by H007 bridge, filtered by C006 4,700uF 63V cap and goes to output amp board P700.
Where have you seen any regulation?

The regulated 35V feeds P500, P300 and P900 but none are the output amp.

What you could do is disconnect one of them at a time and see if the voltage goes back to 35V or so, then you woud know who loads it.

[thirtiesradio]

Sorry Mike. I linked the 2220 schematic and mine is the 2220B. Here is the correct service manual with the schematic. You regulate the voltage with R808. Looks like it feeds several boards.

http://akdatabase.org/AKview/displayimag...m=1&pos=45

[morzh]

Yes. But, again, the power to the output amps is not regulated, it is created with H801-H802 bridge with centertap from xfmr Og-Og winding and tfhen fitered to create +/-35V by C003-C004.
35V feeds other amps.

Same as I said above, if you want to find out why it is low. Start disconnecting loads. Find out which one brings it down, then investigate.

[thirtiesradio]

OK Mike will do. Thank you.

[thirtiesradio]

Well I disconnected all leads one at a time and the voltage was still the same (within a volt) so it's in the power supply. I've heard that you can use the diode setting on your multi meter to check transistors? Is that true? All diodes checked out good.

[morzh]

Check:

1. H806 Emitter (0r H807 BAR) - should be 14V.
2. H806 Base - should be 14.7V
3. H805 Base - 35.7V
4. H805 Collector - 41V

[thirtiesradio]

Hi Mike. Here's the DC voltages I get:

805 E= 12.75 V
805 C= 50.25 V
805 B= 13.07 V

806 E= 6.8 V
806 C= 13.2 V
806 B= 7.51V

Thanks Mike.

[morzh]

OK. Your 806 E/B is wrong.
This is dictated by H807 Zener and it has to be 14V.

Could be

Bad 807
Bad R805
Bad C807/809

But first,

There is wire soldered to J808 contact. Remove it, see if 806 E/B voltage returns o 14V and 35V is restored. If yes, trace the wire, see who loads it.

[thirtiesradio]

Hi Mike.
Finally getting time to work on this again.

On your last note where you wrote "bad 807" were you refering to R807, H807 or C807?

There are 4 wires on the J808 contact. I removed them all and E/B voltages on H806 are 16V/15V.

Here's what I checked/replaced.

H807 Zener diode replaced
H806 transistor replaced
R805 checked OK
R807 checked OK
C809 Replaced in recap

C807 is a ceramic cap .04 uf. Can I replace it with a film cap? They list C806 as a .047 film and C807 as .04 ceramic. Why did they use a ceramic cap here?

Thank you Mike!

[morzh]

I cannot find the link, those you have before do not show these parts at all. No zener, no transistor. I meant the zener.

Before you tell me where the correct sch is I cannot help.

[thirtiesradio]

This is the link I was using  http://akdatabase.org/AKview/displayimage.php?album=1&pos=45

[morzh]

OK. Working now. Somehow when I go to the link it shows a sch and when I open it it is different. I have to click on the main PDF, and then the whole manual appears and this is the one.

You should've disconnected those wires before you did the replacements.
Don't jump the gun.

Now that you have disconnected it and your voltages seem OK (please be accurate with description), your B voltage should be higher the E, so when you said "E/B voltages on H806 are 16V/15V." you might've meant the opposite, otherwise it is not normal. YOur E should be lower than B.

If this is the case, and It is "B/E" = 16V/15V then see what your 35V (J812) looks like.
If it is 35V, then start connecting the wires to J808 one by one, until you find the one that screws it.