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Author Topic: polytone 102 schematic  (Read 532 times)

ilyaa

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polytone 102 schematic
« on: December 26, 2017, 11:58:51 PM »

the amp I have does not jive with any of the schematics ive found online.

(http://el34world.com/charts/Schematics/files/polytone/Polytone_Schematics.htm)

someone has definitely dug around in here before. first warning sign was that both output transistors had been replaced with 2n3055. I know occasionally youll run across a power amp that uses two NPNs but this amp has +30 and -30 rails and none of the polytone designs I've seen resemble a dual NPN thing. there was also a shorted driver. but before I dig too deep id love to see a schematic...

this amp has the proper To-3 heatsinks for the power amp. it says Polytone 102 70W on the back. its a 1x12 combo. the power amp pcb has a pair of NPN/PNP drivers for each output. currently they are 2n3053 and 2n4037s. other differences from existing schematics:uurather than being .15 ohms, the resistors on the output are 15 ohms. and rather than being 100 ohms,uthe resistors on the bases of the output transistors are 2.2K

oh yeah and important detail: there is an 8 pin TO-5 old-style IC at the input of the power amp. unfortunately all the text has rubbed off of it....

I can post a pic soon - any thoughts in the meantimeu
« Last Edit: December 27, 2017, 12:08:21 AM by ilyaa »
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ilyaa

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Re: polytone 102 schematic
« Reply #1 on: March 07, 2018, 02:33:59 PM »

anyone have any thoughts on this?

here's the thread from ampage - got into it a bit deeper but still no dice...

http://music-electronics-forum.com/t45698/
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g1

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Re: polytone 102 schematic
« Reply #2 on: March 07, 2018, 10:02:59 PM »

There was question about whether that can was possibly a dual transistor (yes they made them in cans).
I see 2 leads of the can are not connected to anything.  Have you drawn out where the other leads are going?  Does it resemble the circuit with the dual transistor?
If not, there don't seem to be any schems close to what you have there. 
So you will need to draw out at least the can area, and possibly the whole circuit.
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ilyaa

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Re: polytone 102 schematic
« Reply #3 on: March 08, 2018, 01:04:31 PM »

gotta be honest - i think id be better off just rebuilding the power amp for this thing - the can does not seem to be matching up with any of the schematics - and even if it did who knows if that can is still good...

any recommendations for a simple single PNP/NPN pair output design? would rather make something that doesnt involve a dual can! +/- 30V rails...right now i have an MJ15023/2N3055 situation (what i had laying around) but id be willing to work with whatever - would like to get this thing working!
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