Leestereo's Restoration and Upgrade Of A Marantz 2325

I was going to ask you Steve did you replace those grey tin film caps I see on other rebuild that lots of people are not replacing them , just curious about the sound impact,my 2325 is not working until I rebuild it so I can't tell what a 2325 sounds like
Denis
 
I was going to ask you Steve did you replace those grey tin film caps I see on other rebuild that lots of people are not replacing them , just curious about the sound impact,my 2325 is not working until I rebuild it so I can't tell what a 2325 sounds like
Denis
Which board are you referring to? I can check my parts list. Don't remember off hand if I did or didn't.
Steve
 
I have some on the P-400 C-401-2 and I am reading about high end Philips orange drops I was thinking on using some on the P-700 C-701 I hear these put out fantastic sound
 
Hello Leestereo, in your post for upgrading the P700 power amp for the Marantz 2325, you specify that H701 and H702 are a matched pair. Where do you purchase matched pairs?
Thank you in advanced. 'O'Frank
 
OFrank, those transistors are dirt cheap. You buy at least 20 or so - more if possible - and test them on an hfe tester. The Chinese component testers you can get on the bay will digitally display the hfe or many cheap (think Harbor Freight) DMM’s have an hfe test mode. Measure a bunch of the transistors and pick two close together in hfe - say a difference of 5 or less. Less is better.
Steve
 
Phono Stage (P400)

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P400 board in original state
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P400 board restored/upgraded
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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.

I am getting ready to restore my Marantz 2325. I have been reading a lot of forums (this seems to be the best) about doing the restoration. In doing my research for the P400 phono pre-amp. Everything I read and have seen on YouTube videos it spec's that the 2SC1344 and 2SC458 transistors are replaced with KSC1845 which has half the Ic of the original transistors. I have found other transistors that are a much better match to the original transistors. Therefore, I am wondering why the KSC1845 is used?

The Fairchild BC548C is almost an exact match with a higher gain. Also, the NTE199 also seems to be a better match. Although the NTE is a higher price, the Fairchild is about the same price as the KSC1845.

Again why is the KSC1845 used over others?

Thank You in Advance! 'O' Frank
 
I would hesitate to use NTE in anything I care about.
Does the BC part have the same basing (collector in the center) as JIS parts?
I have used KSC1845 'F' gain code to replace 2SC458 transistors many times, the lower Ic is not a factor here, low noise is.

Tom
 
I used the KSC1845's in my 2325 restoration as recommended in this thread. The phono section sounds great to me and is very quiet. But I do have a situation where the volume has to be turned up 15-20% if you go from tuner to phono. I didn't listen to the unit other than just to confirm it worked before the restoration, so I never knew if this volume difference existed before the rebuild. Your info makes me wonder if the gain difference is the cause. Regardless, I'm very happy with the sound and I have more volume available than I am willing to use.
 
I...The phono section sounds great to me and is very quiet. But I do have a situation where the volume has to be turned up 15-20% if you go from tuner to phono. I didn't listen to the unit other than just to confirm it worked before the restoration, so I never knew if this volume difference existed before the rebuild. Your info makes me wonder if the gain difference is the cause...

The transistor gain (hFE) specifications for H405/406 does not set the sensitivity of the phono circuit per se, it is the feedback loop that controls the overall gain. Also the "B" gain specification for the 2SC458L at H405/406 is 100-200, which is actually lower than that specified for the "F" gain specification of the KSC1845: 300-600.
 
Phono output level will always be lower compared to tuner and tape levels due to the lower voltage output; cartridge output levels have very small voltage increments...some less than 1 mV. That will definitely show up on the volume level when trying to match output for output per se.

But still, you’re on to something interesting with matching transistor gain output levels. Sounds like many techs here essentially found a good replacement that works well, drops the noise floor a little, but sacrifices a little output gain.

Has anyone tried slightly different output gain transistors in those spots on P400? I wonder what they would sound like as a comparison? Too hot? Increased noise floor? I’ve never heard the originals, so haven’t experienced the notorious problems they are known for. Just curious...
 
Never mind...

Thanks Leestereo for the explanation!

In the feedback loop, how would increase gain output slightly higher, without adding more noise? Or is it possible without changing the RIAA curve?
 
...In the feedback loop, how would increase gain output slightly higher, without adding more noise? Or is it possible without changing the RIAA curve?

Decreasing the value of R412/R413 would increase gain; a small decrease from 620ohm e.g., 560ohm or 470ohm will give a small increase in gain and would not significantly impact the RIAA correction.
 
The phono preamp in most older gear was designed to boost the output of a typical (what ever that is) magnetic phono cartridge to a line level signal. When CD players came out, their output was around 2VRMs instead of the old .775VRMS line level standard.
Most FM radio stations have volume limiters to keep their transmitter modulation near 100%, so it's as as loud as possible.

It's no wonder we have to crank up the volume when we want to play a record.

My 2 cents.

Tom
 
possibly looking for one of the black 2325 marantz faceplates whoever sells them let me know if available and cost thx
 
AK member "ragstoriches" brought in a very nice Marantz 2325 for some restoration and upgrade work.

The restoration/upgrade included the following:
1. Replacement of the power supply electrolytic capacitors with low ESR types (increasing capacity where appropriate and physically possible).
2. Replacement of the signal path electrolytic capacitors with film types (whenever possible) or bi-polar electrolytic types.
3. Upgrade original polyester film capacitors to polypropylene film types (as appropriate).
4. Replacement of the signal path ceramic capacitors with C0G types.
5. Replacement of the failure-prone 2SC458 and 2SA722 transistors.
6. Replacement of the output relay.


Power Supply & Relay Board (P800)

The P800 board contains the regulated power supplies as well as the protection circuit.
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P800 board in original state
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Components removed
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Board cleaned of glue residue
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Restored and upgraded board
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The DS-131B dual diodes, H808 and H809, were upgraded to high current, soft recovery types:
NXP BYQ28E-200,127. The capacitor C803 is the main filter for the regulated supplies and the original 470µF/63V capacitor was replaced with a 1200µF/63V low ESR type. Similarly, capacitor C806 filters the 35V and 19V supply, and the original 220µF/63V capacitor was replaced with a 680µF/63V low ESR type. The large 150 ohm/5W dropping resistor, R801, that feeds C804, was replaced with a physically smaller 150 ohm/7W one to allow better air flow around the surrounding components. The C804 capacitor that filters the 14V supply was replaced with a 680µF/63V low ESR type. Capacitors C805, C807 and C809 are on the base of the regulator/pass transistors and were replaced with low ESR types: 470µF/35V, 330µF/50V and 22µF/50V, respectively.

Capacitors C811, C812 and C813 are used in the protection relay circuit and were also replaced with low ESR types: 22µF/63V, 47µ/25V and 220µF/35V, respectively. The protection relay (L801) was replaced with an OMRON LY2-0-DC24, which is a drop-in replacement for the original type.

Your replacement for R801 is it a wire wound?
 
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