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Old 4th Jan 2021, 8:38 pm   #1
allyson114
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Question Help with a transistor ID please

Good evening folks and a happy new year to you all. My husband has 2 power tab transistors, 1 red case and 1 green case- both mounted on heat sinks. The red case is an NPN 188 48929-2 7831, the green case is a PNP 188 48932-2 7904, they are in a Rock Ola jukebox on the "driver boards". Can't find any reference to the numbers anywhere. Can any one help at all with a replacement that we could use? thank you, x
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Old 4th Jan 2021, 9:30 pm   #2
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Default Re: Help with a transistor id please

THey look to be 'house numbers' literally stock numbers used by an equipment manufacturer.

7831 and 7904 are likely to be date codes Year 79 (1979) and week 04 for example.

The most likely manufacturers are RCA and Motorola. A good photo might let that guess be refined a bit more. There are style details in the moulding and even the typeface that can be give aways.

Failing that, given the circuit diagram, some reverse engineering can be done and suitable devices suggested.

In transistor amplifiers it is unfortunately common for one failed transistor to take a number of others with it. If you try replacing one at a time, the dead ones take out the new ones and you can get locked in an infinite circle.

The escape from this is to test them all and replace all faulty ones without applying power until they've all been changed.

It takes a bit od self-discipline to go the long way round, but it's a lot quicker than a short-cut

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Old 4th Jan 2021, 9:31 pm   #3
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Default Re: Help with a transistor id please

Those are Rockola part numbers so unlikely you'll find the data. They should be replaceable with any transistors in the same package. Important ratings are Vcb / Vce > 80V, Ic > 1A, and check SOE curves to ensure they are rated for audio use. e.g. BD239C/BD240C
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Old 4th Jan 2021, 9:34 pm   #4
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Default Re: Help with a transistor id please

They sound rather like a complementary pair of output transistors. You could probably guess at something suitable if you have a rough idea of how much voltage/current they have to handle.

Have you got any service data? A circuit showing their application would be handy!
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Old 4th Jan 2021, 11:32 pm   #5
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Default Re: Help with a transistor id please

Are you able to provide the Rock-Ola jukebox model number, driver board number and amplifier number?

This would help us to find a schematic and maybe a working voltage.

The 'power tab transistor' may be a transistor in a TO220 package.
Are you able to confirm this?
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Old 5th Jan 2021, 12:09 am   #6
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Default Re: Help with a transistor id please

Here's the driver board I think the OP is referring to, it's the power amp transistor driver board (2 boards for stereo).

Circuit ref. Q5 and Q6 (left and right).
Early boards use a TO-202 package, later ones a TO-220 package.

No clue as to the specs but I'm sure a jukebox forum would be lucrative. I suspect a TIP41C/TIP42C or other audio driver pair would do plus a bias check.

If the output transistors are 2N3055 and have failed, modern ones may oscillate and blow up without modification, eg base stopper.
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Old 5th Jan 2021, 12:30 am   #7
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Default Re: Help with a transistor id please

Likely the output devices will have house numbers too, unless any have been replaced, but 2N3055 are likely to have been used however they've been marked.

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Old 5th Jan 2021, 1:50 am   #8
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Default Re: Help with a transistor id please

From the Jukeboxaddicts forum

Rockola 474
Q5 part# 48929
Q6 part# 48932
Q7 part# 48931
Q8 part# 48931

Driver transistors TIP 41C and TIP 42C.
Power transistors ECG 181.
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Old 6th Jan 2021, 12:11 pm   #9
allyson114
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Default Re: Help with a transistor ID please

Thank you for your help so far-am sending 2 pictures that may help in this latest challenge for you, xx
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Old 6th Jan 2021, 1:58 pm   #10
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Default Re: Help with a transistor ID please

I may be well off the mark here, but those 'wire' type pins look very Motorola to me.
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Old 6th Jan 2021, 1:59 pm   #11
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Default Re: Help with a transistor ID please

In appearance, they look like GE D45H11 (green, PNP) and D44H11 (red, NPN) transistors.
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Old 10th Jan 2021, 2:33 pm   #12
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Default Re: Help with a transistor ID please

I'm going to be boring and suggest replacing those with TIP41/2 C's and also to be aware that the bias setting may be out of range and require a tweak of the series resistor to the preset. In any case, the preset should be turned to MAX resistance initially which will give minimum bias.

Use of a DBT (bulb tester) would be advisable as well as this can save destruction should any further problems be lurking.
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