Motorola (?) RingEmitterTransistor MN25 / MP 25 - diyAudio
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Old 13th November 2005, 08:21 AM   #1
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Default Motorola (?) RingEmitterTransistor MN25 / MP 25

Hi,

any information about those transistors or substitutes Sanken (?)
Seem to have been used in Pioneer M25 amp.
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Old 13th November 2005, 11:35 AM   #2
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Not likely.

MN25 was a TO3 germanium transistor made by Motorola.
MP25 a Russian made TO5 device (ELORG= elektron org. teknika in Moscow)
MN25 and MP25 were probably the internal Pioneer device numbers, M25 NPN and M25 PNP.
Only ones producing ringemitters were Toshiba and Sanken, production of high power ringemitter transistors started before Pioneer started production of the M25 in '79.
Later production Toshiba ringemitters had the identical MT200 casing and color as Sanken devices.

Pioneer produced the open-style chassis 30 watt class A M22 end of the 70s, followed-up by the partial class A M25.
Both looked practically identical, seen quite a few of these machines in France.

www.visi.com/~jweeks/stuff/pioneer/#series20
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Old 13th November 2005, 12:42 PM   #3
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Thanks,

the matter is, if I get a broken M25 and need to replace output RETs, is there a possibility to get those or use Toshibas or Sankens ?
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Old 13th November 2005, 03:04 PM   #4
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The ringemitter devices used in the M25 and A27 integrated amplifier were TO3 models.
Fat chance that you can find those, MT200 Sanken's will have to do.
Means redrilling the sinks with the MT200 pattern.
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Old 14th November 2005, 10:26 AM   #5
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Here is a picture of the output section of the A-27 integrated amplifier model (found it on a Pioneer series homepage somewhere)
2 NPN and 2 PNP TO3's per channel.
Supposedly the A-27 used the same devices as the M25 did, and much of the circuit concepts of the M25 and C21 preamplifier.
Pioneer used the big casing Sanken multi-emitter devices in the later M series power amplifiers.
Attached Images
File Type: jpg pioneer a-27 output devices.jpg (9.2 KB, 182 views)
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Old 14th November 2005, 10:36 AM   #6
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Later model multi-emitter devices
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File Type: jpg ret.jpg (65.2 KB, 163 views)
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Old 14th November 2005, 10:40 AM   #7
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revised casing Toshiba ret's
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File Type: jpg mt200 2sa1095-2sc2565.jpg (22.5 KB, 156 views)
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Old 14th November 2005, 11:13 AM   #8
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Thanks, so I have to look for a A27.

Your first picture does not load completely.
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Old 14th November 2005, 06:00 PM   #9
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found the homepage i got the picture from again:
http://www.silverpioneer.netfirms.com/a27_amplifier.htm

These amplifiers have collectors value, and you would probably need 2 of the A-27 amplifiers to have enough output devices to repair an M25.
Fixing an M25 with modern Sanken devices will not keep the amplifier original, but a lot easier and big Sankens are very rugged.

The M model is a lovely design, wouldn't mind having one myself.
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Old 17th November 2005, 12:14 PM   #10
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Just got the amp and - huh - all output transistors measure around 0,5 V from case to one pin and another 0,5 V between pins with diode tester.
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