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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 15th Jul 2018, 7:25 am   #21
Jac
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Default Re: “New” AF126 duff

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the Tesla OC169 & OC170. (photo attached on right hand side)
That's an interesting looking OC170.
The Philips/Valvo/Mullard version has a housing like the AF114/5/6/7/8.

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Old 15th Jul 2018, 11:48 am   #22
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Default Re: “New” AF126 duff

Some OC170's only had three leads, but I've never been able to find data for them.

https://www.vintage-radio.net/forum/...ad.php?t=69688
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Old 15th Jul 2018, 12:11 pm   #23
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Default Re: “New” AF126 duff

Sorry Graham that my photo is not too clear. This OC170 does have 4 wires.
I can't make a new photo, since I used it in my Sony to replace a defective 2SA70.

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Old 15th Jul 2018, 2:01 pm   #24
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Default Re: “New” AF126 duff

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I find it a bit of a shame that the only transistor in the world which had about the same sized case and the linear pin array matching the AF11X transistors and the same electrical properties and was resin filled and free from the whisker effect was the Tesla OC169 & OC170. (photo attached on right hand side)
I'm sure someone has written about it before, but were the Matsushita equivalents of the AF11x also plagued by whiskers?
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Old 15th Jul 2018, 2:29 pm   #25
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Default Re: “New” AF126 duff

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Some OC170's only had three leads, but I've never been able to find data for them.

https://www.vintage-radio.net/forum/...ad.php?t=69688
I have the Philips data sheets, they are all 4 lead types, very detailed with circuit examples and graphs on OC169, OC170 and OC171 dated March 1960.

169 was for IF amp in AM & FM receivers ft 70MHz.

170 mixer osc SW and MW radios & 10.5MHz IF's, also ft 70MHz.

171 shown in the manual as 100MHz grounded base amplifier.

All characterized by very low collector-base capacitances and not requiring neutralization when used as IF amps.

Wonderful transistors, but unfortunately identical physical construction to AF114-118 and doomed to tin whisker death.

AF178's make great replacements for these too.
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Old 15th Jul 2018, 2:57 pm   #26
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Default Re: “New” AF126 duff

They are basically the same transistor as the AF114-7 though the stated ft is a bit lower. I suspect Mullard were getting a lot of variation in early production and tested each one, marking them accordingly. By the time Mullard switched to Pro-Electron codes they were getting much more consistency with reliably higher ft ratings.
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Old 15th Jul 2018, 4:08 pm   #27
FiveBobRepairs
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Default Re: “New” AF126 duff

Glad to see my (deserved) misfortune with that AF126 has inspired some interesting peripheral debate.

Maybe also of interest, in addition to my current endavours, I recently swapped an AF114 for an AF124, in the fm tuner module of a Roberts R700. In that case, it transpired the pcb couldn’t have been designed better for the AF124. The pcb holes under the original AF114 were in a square, and in the correct AF124 sequence.

Makes me wonder whether somebody involved in the design might have had an incling that an AF124 might one day come to live there.
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Old 15th Jul 2018, 11:44 pm   #28
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Default Re: “New” AF126 duff

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That's an interesting looking OC170.
Jac
Yes, those Tesla ones had a near identical physical size to the original OC170/AF114 etc, but a small flare or lip on one end of the case and filled with a lovely looking green resin rather than the silicone grease of the Philips/Mullard types. Though I have never actually cut a Tesla one open yet, as all that I have are ok so far. But for the most part at least, resin filled germanium transistors appear to be immune from whiskers.
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