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MARANTZ model 15 diode identification

G

Gmanfro

New Member
Trying to identify two diodes for an early 15 to a replacement diode number. I have searched everywhere and can't find a cross. The two diodes are
1. CR102, 108 shows MR2360 and need a replacement number
2. CR103, 105, 106, 107 shows BTR1557 and need a replacement number
Any help would be much appreciated. Thanks in advance...

Jeff
 
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Could you post a pic of the schematic, at least for the sections where those diodes are located?
 
Gmanfro said:
Trying to identify two diodes for an early 15 to a replacement diode number. I have searched everywhere and can't find a cross. The two diodes are
1. CR102, 108 shows MR2360 and need a replacement number
2. CR103, 105, 106, 107 shows BTR1557 and need a replacement number
Any help would be much appreciated. Thanks in advance...

Jeff
Click to expand...
This place list 365 of the MR2360 in stock: https://www.dfsales.com/
 
Here is a pic of the schematic. After opening the unit up and looking at the diodes and measuring the voltage drop it seems like the CR102/108 (MR2360) might be a plastic diode rectifier, maybe I can use a 1N4004-1N4007? The CR103, 105, 106, 107 (BTR1557) is a glass Si diode with a marking (GE 125), which I could not cross, and I am thinking it is just a standard 1N4148? Since this is a mid-late 60's amp the BTR1557 might have been the old 1N914 equivalent which is now a 1N4148 but not positive.

Just a note that the BTR1559 is able to be subbed with 3-1N4148's in series. So I am thinking the BTR1557 is just a 1N4148.

Thanks ramjet for a lead on the MR2360. That is an option if I can not find a modern cross for the old number diodes.

MARANTZ 15.png
 
I did find a schematic with voltages which should help identify what diodes I can use for replacement. Also here is a chart of the voltages at the transistors.
 

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I think your proposed subs would be ok but somebody with more experience on these amps might have better ideas. Looks like CR02/08 need to be matched which is a little unusual. Not sure if just matching the forward voltage drop is enough?
 
Thanks Brian1970 for bringing up diode matching. Yea looking at the schematic and manual it seams like the CR106/107 is limited to +/- 1 diode drop. Also looking at the boards those two diodes seam to be different slightly in color compared to the CR103/105 inside the glass so they may be specially matched (pinkish instead of orange like 1N4148 and CR103/108). I will match them on the curve tracer to get them as close as possible.

Thinking of what diodes were available back then there sure wasn't a wide selection so the CR102/108 may have only been a 1N4001/02 but I will try 1N4004 (over kill but that's me). From what I deduct from the manual CR102/108 are doing different things in the circuit so I don't think those need to be matched.

Wish I would have been able to cross those original numbers over to be positive, but sometimes that's how it goes. Maybe someone will chime in before I get to it. Still getting my list of parts to order together.
 
I think I misread the notes on the schematic. The matched note looks like it applies to a couple transistors which makes more sense.
 
Yes I do know some of the transistors need to be tightly matched especially Q102/103. IIRC they should be low beta and matched VBE. I normally match drivers and outputs on everything I do.
 
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