Restoration and Upgrade of a Marantz 2235B Receiver

Leestereo

Super Member
A very nice Marantz 2235B receiver was in for a complete restoration and upgrade. Here are some pictures of the 2235B as first received:















The restoration/upgrade plan included:
1. Replacement of all of the power supply electrolytic capacitors with 105°C, low ESR types (increasing capacity where appropriate and possible).
2. Replacement of all of the signal path capacitors with either film types or C0G types, as appropriate.
3. Replacement of the vellum behind the tuner dial and meters.
4. Replacement of the protection relay.
 
Those 330uf caps on the PS board look like they got a little warm.

Yeah, just a bit...they're pretty close to the 150ohm 5W resistor and it runs very hot. The plastic sleeve on the bottom of the capacitors had also shrunk.
 
Yeah, just a bit...they're pretty close to the 150ohm 5W resistor and it runs very hot. The plastic sleeve on the bottom of the capacitors had also shrunk.

Maybe hang that thing off the board over the chassis?
 
The heatskank is fastened to the chassis so it works very well. Looks like some of those PS caps indeed grew out of their "pants"! :D Nice model being redone by a great tech. :thmbsp:
 
Power Supply/Relay Board (P800)

The P800 board supplies the regulated voltages (13V and 35V) for the low level stages. The capacitor C801 is the main filter for the 35V supply and the original 220µF/63V capacitor was replaced with a 470µF/63V Nichicon PW low ESR type. Similarly, capacitor C805 filters the 13V supply, and the original 330µF/50V capacitor was replaced with a 680µF/50V Nichicon PW. The large 150 ohm/5W dropping resistor, R807, that feeds C805, was replaced with a physically smaller 150 ohm/7W one to allow better air flow around the surrounding components. Capacitors C802, C804 and C806 are on the base of the regulator/pass transistors and were replaced with Nichicon low ESR types: 220µF/50V, 47µ/50V and 470µF/35V, respectively.

Capacitors C807, C808 and C809 are used in the protection relay circuit and were replaced with low ESR types: 10µF/50V, 47µ/25V and 220µF/35V, respectively. The L801 protection relay (L801) was replaced with an OMRON MY2-02-DC24 which is drop-in replacement for the original a MY2Z-02-DC24 type.





 
Phono Stage (P400)

The stock capacitors in the input high-pass filter (C401, C402) were 2.2µF tantalum capacitors and these were replaced with 1.0µF Panasonic stacked polyester film capacitors. The resultant F3 of the high-pass filter with the replacement film capacitor is more than adequate at ~1.4Hz. The electrolytic capacitors C407/C408, which determine the low end roll-off of the RIAA equalization, were low leakage 22µF/25V. These were replaced with 220µF/25V Nichicon KW Audio Grade types. The stock capacitors in the low-pass filter (C403, C404) were ordinary 200pF ceramic capacitors; these were replaced with 180pF C0G capacitors. The capacitors (C411,C412) which shunt the emitter resistors for H403/H404 were originally 47µF/16V and these were replaced with 100µF/35V low ESR types. The local filtering/decoupling capacitor, C421, was a 100µF/50V and was replaced with a 220µF/50V Nichicon low ESR type.



 
Thanks for the Schematics and discussions of the their operation and relevance to the replacement parts. A very instructive thread. I'll be anxious to see how you like the sound of the results - especially since the "b" series don't seem to get much love. It looks like a fairly easy layout to work on - am I seeing it correctly? Any upgrades contemplated?
 
Never thought about upping the 13v/35 filter supply caps in uf, just upped the temp rating and lower esr specs. Those 150ohm 5 watt resistors do get toasty. Now you have me staring at several restored units in my collection begging to be tweaked :)
-Lee
 
...especially since the "b" series don't seem to get much love.
Despite the "B" designation, this particular Marantz model predates the ones with the silver tuning dials. In this case, the only difference I can see between the 2235 and the 2235B models is the addition of a signal strength meter, everything else looks identical.

It looks like a fairly easy layout to work on - am I seeing it correctly? Any upgrades contemplated?
Yes, the layout of the boards makes this one a relatively easy one to work on. Note that the preamp and the main amplifier boards don't have detachable connectors like those used in higher models; but there is enough wire slack to work on them in situ. Also, the phono is mounted on the underside, but again there is enough wire slack to work on this board without too much trouble.
 
Despite the "B" designation, this particular Marantz model predates the ones with the silver tuning dials. In this case, the only difference I can see between the 2235 and the 2235B models is the addition of a signal strength meter, everything else looks identical.

I'll agree with you there. That's the only difference I could find in the 2235.

I have a restored 2235B. They're pretty nice sounding receivers all done.
 
Tone Amp Stage (PE01)

Signal Path Capacitors:
In the restoration/upgrade of the Tone Amp board, all of the signal path capacitors replacements were either film or C0G types.

The input high-pass filter capacitors (CE01, CE02) were originally 0.22µF polyester film types and these were replaced with 0.27µF Panasonic polypropylene films. The output capacitors of the first gain stage (CE05, CE06), were 4.7µF/25V low leakage electrolytic types and these were replaced with 4.7µF/50V WIMA stacked polyester film types.

The capacitors (CE07, CE08) in the low pass filter for the treble tone control circuit were ordinary 100pF ceramic types and these were replaced with C0G capacitors of the same value. The stock capacitors in the input high-pass filter (CE19, CE20) of the second gain stage were 1.0µF low leakage electrolytic capacitors and these were replaced with 1.0µF Panasonic stacked polyester film capacitors. Similarly, the output capacitors of this gain stage were low leakage electrolytic types and these were replaced with 3.3µF/50V WIMA stacked polyester film types (CE21, CE22) and 1.0µF Panasonic stacked polyester film capacitors (CE23, CE24). Note that CE21 and CE22 are mislabeled as 33µF in the Marantz 2235B schematic.

Non-signal Path Capacitors
The local DC filtering capacitor for the preamplifier stage (CE25), was originally 220µF/35V and the replacement was a 470µF/35V low ESR type. Similarly, the original decoupling capacitors for the first gain stage (CE03, CE04) were 10µF/35V and these were replaced with 22µF/50V low ESR types.



 
I am lovin' the big boy R807, great upgrade and solution. When they run hot I had been replacing with new and flyin it a little high.

As always there is so much to be gleaned from your rebuilds, especially the why/how of each location.

I know this is not yours but as of late on the PS and or a protection board I have been replacing the 2SC945's. (H803/H805)

To get the full effect of the films and C0G's you are replacing it is all about getting rid of grit/grain especially P/S originated I would also replace the DS131B's (H808/H811) with MUR1620 type.









Power Supply/Relay Board (P800)

The P800 board supplies the regulated voltages (13V and 35V) for the low level stages. The capacitor C801 is the main filter for the 35V supply and the original 220µF/63V capacitor was replaced with a 470µF/63V Nichicon PW low ESR type. Similarly, capacitor C805 filters the 13V supply, and the original 330µF/50V capacitor was replaced with a 680µF/50V Nichicon PW. The large 150 ohm/5W dropping resistor, R807, that feeds C805, was replaced with a physically smaller 150 ohm/7W one to allow better air flow around the surrounding components. Capacitors C802, C804 and C806 are on the base of the regulator/pass transistors and were replaced with Nichicon low ESR types: 220µF/50V, 47µ/50V and 470µF/35V, respectively.

Capacitors C807, C808 and C809 are used in the protection relay circuit and were replaced with low ESR types: 10µF/50V, 47µ/25V and 220µF/35V, respectively. The L801 protection relay (L801) was replaced with an OMRON MY2-02-DC24 which is drop-in replacement for the original a MY2Z-02-DC24 type.





 
...as of late on the PS and or a protection board I have been replacing the 2SC945's. (H803/H805).

Are you seeing 2SC945 failures? Are you replacing with same?

To get the full effect of the films and C0G's you are replacing it is all about getting rid of grit/grain especially P/S originated I would also replace the DS131B's (H808/H811) with MUR1620 type.

I was considering using the MUR1620, but there seems to be some reports (on DIY Audio) that some batches may not be "soft recovery" and added more noise than regular diodes. This was a while ago, so I don't know if this is still the case; or was it the result of using of counterfeit parts.
 
The 863-MUR1620CTG's I have here are from Mouser, I have used them and do not know of any problems. I have also used Qty 2 of Mouser # 511-STTH1R02 and joined C-C.

On the 2SC945's in the Pioneer rebuild world they are replaced on the P/S and or protection board. (as we in Marantz replace 2SC458's)

I am pretty sure I used KSC2383YTA but will need to check my notes. You may want to do at least the one in the relay circuit.:D
 
FM MPX (P300)

The stock local filtering/decoupling capacitors, C327 and C328, were both originally 220µF and the replacements were 470µF low ESR types. The signal path capacitors in the output stage, C323, C324, C325 and C326 were originally tantalum electrolytic capacitors and these were replaced with Panasonic stacked film capacitors of the same capacity. Similarly, the 3 small non-polar electrolytic capacitors for the HA1136 MPX IC (C307, C308 and C309) were replaced with Panasonic stacked film capacitors of equivalent capacity. All other electrolytic capacitors were replaced with low ESR types of the same capacity, but with higher voltage ratings (typically 50V capacitors were used).



 
The resistor standoffs are the originals and are ceramic; Mouser and Digi-Key have standoffs but only in nylon, brass or aluminum.
 
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