Marantz 2325 Phono problem

[Chris Lauver]

Hey guys, I am having an issue with my Marantz 2325 while listening to vinyl. This unit has had the power supply, tone board and Phono board rebuilt, all switches and pots cleaned, and all voltages set to service manual specs. The issue is only when the amp is in phono mode. I will play an album and it sounds great, then out of nowhere it will make a pop or crack sound like the record has a scratch in it, but the record is fine. It will play fine for a while, then again out of nowhere a pop/crack sound. It may do this only two or three times during a whole album. Also, when I go to power off after playing for a while, there is a pop in both speakers. It does not pop when turned on and it only pops on shut off after it has been playing a record for a while. It has none of these issues in any other mode, only phono. Also need to mention, I have tried two different turntables and same problem. Thanks, any help is much appreciated.

 

[Chrisxo55441]

did the transistors get replaced on the phono board. the original 2SC458 are known to be problematic

 

[catrafter]

Also replace any 'epoxy' gob diodes, the two by the last transistors on the phono amp with ONE 1N4148 each, the one near the two trim pots with TWO 1N4184's in series.

Tom

 

[Chris Lauver]

Thanks, I am pretty sure these have all been replaced, but I will check for sure.

 

[Chris Lauver]

Here is what was replaced on the phono board. It is the upgrade posted by Leestereo on this sight.

The stock capacitors in the input high-pass filter (C401, C402) were 1.0µF tantalum capacitors and these were replaced with 1.0µF Panasonic polypropylene film capacitors. The electrolytic capacitors C403/C404, which determine the low end roll-off of the RIAA equalization, were originally 47µF/16V polarized low leakage types. Their replacements were bipolar Nichicon ES capacitors of the same capacity. The local filtering/decoupling capacitor, C413, was a 100µF/35V and was replaced with a 270µF/50V low ESR type (note that the voltage rating should be increased since this capacitor is subject to ~34V). The original polyester film capacitors at the output, C414/C415, were upgraded to polypropylene film types. The failure-prone 2SC458 transistors (H405, H406) were replaced with KSC1845 transistors (note that the pin-order for the original 2SC458 is "BCE" whereas that for the KSC1845 is the common standard "ECB"). The 1S-2473 diodes (H407, H408) were replaced with 1N4148 diodes and the failure-prone VD1212 dual diode (H409) was replaced with a pair of 1N4148 diodes in series.

As for the transistors, there are four other ones on the board that were not replaced (C1344's). Could this be the problem?

 

[wlhd1610]

Any chance your turntable is plugged into the "switched " receptacle on the back and that portion of the push button dpst on-off power switch contacts may be arcing?

Bob

 

[Chris Lauver]

Any chance your turntable is plugged into the "switched " receptacle on the back and that portion of the push button dpst on-off power switch contacts may be arcing?

Bob

No, it is plugged into a power strip. Thanks

 

[petehall347]

does it behave the same with no record playing ? both channels ?

 

[Chris Lauver]

does it behave the same with no record playing ? both channels ?

It is quiet when no record is playing.

 

[petehall347]

see if you can narrow it down to one channel ..

 

[fernarias]

It's probably just static build up on your records. Happens more often in dry conditions, like an air conditioned space. You can add moisture to the air and that will help. I use a carbon fiber record brush and that works for me (ac on all the time and heater on all the time 10 months out of the year, sucks, I want to move). There are many other solutions.


Here's how to test:

 

[hirscwi]

ere's something I picked up a while back but have never used. It relates to the phono section on the 2230, 2245, 2270 and some others. Might be what you need.

Try adding 47 Ohm 1/4 watt resistors in series with the output of the phono preamp board.
Cut the traces as indicated on the bottom of the P700 board and bridge the cuts with the resistors.
Some Marantz models already have this done.

 

[catrafter]

That looks familiar...

Tom

 

[hirscwi]

That looks familiar...

Tom

I probably got it from you but I could not remember...

 

[mbz]

2SC458 transistors (H405, H406) were replaced with KSC1845 transistors (note that the pin-order for the original 2SC458 is "BCE" whereas that for the KSC1845 is the common standard "ECB")

Could you double check this. My recollection/checking indicates both 2SC458 and KSC1845 are ECB. Note if the 2SC458 was the rectangular
outhouse shape (not semicircle TO-92) then it is the bevel face that is the front. The flat face with the lettering (C458) is actually the back (100%
sure)

 

[catrafter]

Most boards are marked with the correct 'outline silkscreen' for TO-92 transistors like the KSC1845.
If not, install them like the ones in this picture. If the diodes circled are epoxy gob types, the one near the two trim pots should be replaced with TWO 1N4148's in series, the other two should be replaced with one 1N4148 each.

Tom

 

[mbz]

Original post is about occassional cracks/pops pointing to 2SC458 as suggested by Chrisxo55441.
If the KSC1845's were installed with incorrect orientation then very doubtful you will get any sound at all.
Suggest you go over the phono board with a magnifying lamp looking for dry solder joints, google has pix's.
Also check wire connections.

 

[Chris Lauver]

Thanks for all help guys. I had a spare phono board and I went ahead and completely rebuilt it with new parts from Mouser. Made sure all transistors and diodes installed properly. Installed it in the unit and same problem. Also noticing a hum getting louder the longer it plays. Tried two different turntables, one is internally grounded and the other has the standard ground wire. Both acted the same. I then connected a ground wire from the chassis of the Marantz to the grounding terminal at the wall outlet and the hum diminished significantly. I went ahead and replaced the power cord with a three prong grounded cord and attached the ground wire to the chassis internally. Made all voltage adjustments 3 times over. So far I have only had time to play for about an hour, but no issues. Still curious as to what the problem was or could be. I will post an update after a longer listening session.

 

[Chris Lauver]

Just wanted to post an update if anyone is interested. After adding the ground and meticulously making all adjustments, I have had no issues. Sounds great.

 

[rBuckner]

Great!