watersgate
New Member
So thanks to all of the great info on this board I just finished my first pass at restoring my 4400. It now sounds absolutely incredible. IMHO it's the best sounding stereo I've ever owned or heard. 
I'll post some pics soon. First I wanted to share a few notes and ask a couple of questions.
Generally speaking, I used FC/FM caps in the power supply and SILMIC II's elsewhere. Many of the original caps were leaking, including in the power supply and the MPX board. It sure sounds better now. I noted the following discrepancies between the service manual and schematic, and what was actually in the unit:
CH05-CH08 (Filter Amp) - schematic shows 4.7uF 25V, actual was 4.7uF 35V
C513-C514 (Vari-Matrix) - schematic shows 3.3uF 50V, actual was 1uF 35V
C304 (MPX) - schematic shows 10uF 16V, actual was 22uF 16V
C250 (FM I.F.) - schematic shows 10uF 16V, actual was 22uF 16V
I used the values shown in the schematic because that's what I had on hand. As mentioned, it sounds great. But I am tempted to plug in the alternate values to see if there's any discernable difference. My model was made in '77, so my guess is that these were tweaks that were made to the design over time but never updated in the manual or the schematic. But who knows...
Also, these caps are shown as polarized in the schematic, but the actual caps were nonpolar:
C401 & C402 (coupling caps on Phono Amp)
C307 & C308 (LPF caps on the decoder IC)
Again, I used polarized caps because that's what I had on hand. My research shows that the common wisdom is that these should be replaced with nonpolar film caps - curious if anybody has a different view, though. As mentioned, it all sounds incredible, including the tuner and the phono stage. So I'm not sure whether to bother changing them out again.
Just a note, for the 1000uF cap in the power supply I used this, it was very expensive but all I could find, and the specs on it are great:
Newark - 98K6827 MAL212018102E3 (Vishay BC)
I used the same filter and bypass caps shown in marantzfan's 4400 restoration thread (which was my main guide for all of this). I also replaced and raised the 150 ohm resistor, I replaced 3 film caps on the power supply that were bubbled from the heat, and I replaced three zeners on the board too. It is rock solid at 35.0 V now.
Question: you guys helped me fix a problem on the power supply that I believe was caused by inadvertently shorting the 35V supply to ground while working on a different board. Both before and after the fix, the power supply has worked perfectly. All the output voltages are perfect. But, there's one (and only one) voltage on the board that is curious...the collector on H811 reads about 46V, while the schematic shows it should be 34V. The H811 emmiter is correct at 13.4V and R802 and R803 measure correctly. So I wonder if maybe it's an error on the schematic? Just sort of bugs me that the board is working but that one value is off. Would love to know if anybody else has a reading on that voltage to compare.
Well that's it for now. Next up is to replace the lamps. I still haven't figured out how to get to them...and I'm considering recapping my SQA-2, has anybody tried that?
Dave
I'll post some pics soon. First I wanted to share a few notes and ask a couple of questions.
Generally speaking, I used FC/FM caps in the power supply and SILMIC II's elsewhere. Many of the original caps were leaking, including in the power supply and the MPX board. It sure sounds better now. I noted the following discrepancies between the service manual and schematic, and what was actually in the unit:
CH05-CH08 (Filter Amp) - schematic shows 4.7uF 25V, actual was 4.7uF 35V
C513-C514 (Vari-Matrix) - schematic shows 3.3uF 50V, actual was 1uF 35V
C304 (MPX) - schematic shows 10uF 16V, actual was 22uF 16V
C250 (FM I.F.) - schematic shows 10uF 16V, actual was 22uF 16V
I used the values shown in the schematic because that's what I had on hand. As mentioned, it sounds great. But I am tempted to plug in the alternate values to see if there's any discernable difference. My model was made in '77, so my guess is that these were tweaks that were made to the design over time but never updated in the manual or the schematic. But who knows...
Also, these caps are shown as polarized in the schematic, but the actual caps were nonpolar:
C401 & C402 (coupling caps on Phono Amp)
C307 & C308 (LPF caps on the decoder IC)
Again, I used polarized caps because that's what I had on hand. My research shows that the common wisdom is that these should be replaced with nonpolar film caps - curious if anybody has a different view, though. As mentioned, it all sounds incredible, including the tuner and the phono stage. So I'm not sure whether to bother changing them out again.
Just a note, for the 1000uF cap in the power supply I used this, it was very expensive but all I could find, and the specs on it are great:
Newark - 98K6827 MAL212018102E3 (Vishay BC)
I used the same filter and bypass caps shown in marantzfan's 4400 restoration thread (which was my main guide for all of this). I also replaced and raised the 150 ohm resistor, I replaced 3 film caps on the power supply that were bubbled from the heat, and I replaced three zeners on the board too. It is rock solid at 35.0 V now.
Question: you guys helped me fix a problem on the power supply that I believe was caused by inadvertently shorting the 35V supply to ground while working on a different board. Both before and after the fix, the power supply has worked perfectly. All the output voltages are perfect. But, there's one (and only one) voltage on the board that is curious...the collector on H811 reads about 46V, while the schematic shows it should be 34V. The H811 emmiter is correct at 13.4V and R802 and R803 measure correctly. So I wonder if maybe it's an error on the schematic? Just sort of bugs me that the board is working but that one value is off. Would love to know if anybody else has a reading on that voltage to compare.
Well that's it for now. Next up is to replace the lamps. I still haven't figured out how to get to them...and I'm considering recapping my SQA-2, has anybody tried that?
Dave
nice job!
