Sunday, April 19, 2015

Another Marantz 2325 Receiver

Marantz 2325 Receiver

Here we've got another Marantz 2325 receiver coming in.  I've said this before, but short of the 2230, this is my favorite Marantz. Very accessible from a technical point of view, but it also has the crisp clean/yet slightly warm tone I associate with the 2230.

Power Supply
Not much in my procedure for this unit has change from the other 2325's I've done. The lyrics were replaced with a high temp, long life Panasonic FC/FR type. Along with the dual diode 131B packages updated to TO-220 MUR1620 type. The relay is a LY-2 Omron, which is still available for a drop in, the regulating BJT's were regreased and the voltage regulated at 35.Vdc. Unlike the 2330 variant, no thermal breakers are led through this supply like the 2330.

Phono Assembly P400
The biggy with the phono assembly is to update several diodes and the H405/406 BJ-Transistors. The 2SC458 BJT's are notorious for developing noise/pre mature failure issues, these are replaced with matched HFe pairs of KSC1845's. The VD1212 glass varistor is updated to two 1N4148 diodes in series. Tantalums and films were updated with Panasonic ECW polypropylene films. Electrolytics were replaced with a single  Nichicon TVX axial and audio grade Silmic II's by Elna. 

Pre-Amp PE01
I really like how easy it is to pull the Pre-amp tone/control sections, this allows you to work with no hassle but also allows you to fully clean and lubricate each potentiometer without fuss. 

The original gray films in this application were update to Panasonic ECW polypropylene films and the original orange films left.  The lyrics were replaced with Silmic II's again and tantalum/low value lyrics were replaced with PET WIMA MKS2 film capacitors, one thing to mind is the footprint, space gets tight with the MKS2's.  Nichicon MUSE BP's replaced the original Bi-Polar Elnas at CE37/38. If you look at my other 2325 posts you can see some photos of the assembly. 

Power Amplifier P700
The amplifier sectionals have a really nice setup here, it uses a molex type power connections and uses a RCA type hookup for the signal path.  The lyrics here were replaced again with audio grade Silmic II's by Elna, the coupling film at C701 was replaced with a nice MKP polypropylene capacitor. Its always a good idea to do a little preventive care and replace the differential pairs at H701/702 (2SA722) with matched HFe pairs of KSA992' transistors. When doing differential pair packages, apply a thin amount of thermal compound and enclose the BJT's together with some shrink-wrap. Note a service bulletin should also be performed if not already done on your series; Updating 718/719H diodes with a single 1N4148. New thermal compound and MICAs were applied as well.

AM/FM Sectionals
In this particular rebuild the customer opted to include all the AM/FM circuits as well. High reliability, low impedance Nichicon PW & Sprague were utilized in this application.  I should note, P600 the Dolby noise reduction circuit isn't applicable anymore. Dolby FM was introduced in the late 70's as unsuccessful noise reduction system, similar to the High Com FM predominate in Germany at the time. 

Extra Curricular 
The buffer stage's lyrics were swapped with audio grade Nichicon FG's and Silmic II's, I recommend updating HH11 to two 1N4148 in series. The PL01 400Hz Osc. PCB was recapped using again, high reliability, low impedance Nichicon PW's.

Last but not least I always recommend replacing the original power switch in these 22XX's series with a DPDT 7A< switch, I like the EG1018-ND and add a X1Y2 safety cap.  The large filters caps were replaced with Nichicon's 18Kuf/75Vdc type, which are a perfect drop in for the 2325/2330. New Vellum paper was applied, warm white LED's and new 33uf electrolytic caps across the meters finishes up the lighting. 

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