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S-300E transistors.

 
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S-300E transistors.

Post by Rebel Rafter » Thu Jan 07, 2016 8:14 pm

Hi, from RR. Does anyone here know anything about some transistors marked as S-300E? They're on a preamp board out of a jukebox which I'm repairing and they're not in my old towers book and they're not in my jaeger book and google isn't much help either. Any help most appreciated. RR.

 
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Re: S-300E transistors.

Post by sideband » Thu Jan 07, 2016 8:51 pm

They could be 'in-house' numbers....in other words, standard transistors that have been renumbered by the Jukebox manufacturer. Thorn used to do this but they issued an equivalents booklet. I suppose it's an American jukebox? Really, if it's only a pre-amp then you'll probably find that standard transistors will do the job. You only need to check that the supply rail is suitable for the device.

As an example, on my old Hi Fi amplifier made by Akai, the pre-amp and driver transistors started to fail. The numbers didn't appear in Towers or any other book I could find. However a check in a standard transistor book showed that BC548's would be suitable in the preamp and BC 328/338 would be OK in the driver stage based purely on the supply rails. It's been working fine for many years. All I had to do was set up the quiescent current.

 
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Re: S-300E transistors.

Post by Rebel Rafter » Thu Jan 07, 2016 11:33 pm

Hi, from RR. It is indeed American, it's a Rowe-AMI R74 from about 1976. I'm only working on the audio side, I'm not touching the mechanism, no chance, I'll leave that to the experts, that bit works thank goodness. I've just got a spare s/h preamp from a place in Middlesex, I think you're right about the in house numbers as all the transistors have got very similar numbers and packages, a bit like TO92's but not quite the same. One has shorted and fried a resistor which still has it's colour code intact, and another transistor has a cracked package. My mate has the manual with the circuits so hopefully the right numbers will be in there. The whole preamp runs on 24 volt so there shouldn't be any problem with voltage ratings but I know some of the circuitry is a bit odd, with features like AVC and a discrete DC volume control, and a fancy feature that boosts the bass at low volume levels. It's all transistor, no chips, but lots of diodes, and it's all silicon apart from one diode. RR.

 
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Re: S-300E transistors.

Post by Terrykc » Fri Jan 08, 2016 12:45 pm

Rebel Rafter wrote: ...  a fancy feature that boosts the bass at low volume levels ...
Known as a Loudness control and traditionally performed by a potentiometer with a tapped track ...

 
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Re: S-300E transistors.

Post by sideband » Fri Jan 08, 2016 2:30 pm

Quite a common feature on the better Hi Fi amps of the 70's in the form of a separate switch. I think Grundig and Philips used a tapped pot so that the bass boost was brought in gradually at lower volumes. Always seemed very effective.

 
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Re: S-300E transistors.

Post by Marconi_MPT4 » Fri Jan 08, 2016 5:28 pm

Hi,
Appears to be an in-house transistor part number of AMI-Rowe. There is a list here where there is a link to a file listing the new Rowe in-house part number 700-300-05. No actual specs, but lists some generic parts at the end of the document.

Cheers
Rich


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