Author Topic: OC75 G2R7 transistors  (Read 266 times)

szec

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OC75 G2R7 transistors
« on: September 05, 2017, 12:56:56 PM »

There are quite a lot of OC75s on ebay labeled only with "OC75 G2R7". All sellers claim that they are Mullard made, but I am not so sure about it. As far as I know they should have "Mullard Made in Great Britain" on them if they are the real deal. Were they made in some other Philips factory outside UK?
Any help would be appreciated.

Bret608

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Re: OC75 G2R7 transistors
« Reply #1 on: September 06, 2017, 07:31:20 AM »
I've got a Philips OC75 at home...let me check it out when I get home this afternoon and see if it's labeled in a similar way to what you're seeing.

FYI, it was way too hissy to use in the Zonk/Mk I-alike I tried to use it in. It sounded like the amp was on fire or something. I had an input cap blend pot on the front end of the circuit that panned from 1n to 100n, and the hiss only went away if that was maxed out at the 100n side. I'll still try it out in a MkII or something. I guess what I'm saying is, be careful and don't set your expectations too high!  :)

szec

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Re: OC75 G2R7 transistors
« Reply #2 on: September 06, 2017, 03:08:48 PM »
Cool, thanks for checking.

I actually decided to give them a try and ordered three from ebay. They have all hfe a bit above 70 and leakage from 400 to 700 uA. I through them into a tone bender mkII circuit and they sounded pretty nice. To get the sound I want I will need something with higher gain though. The fuzz is bit too compressed at the moment. I was quite surprised how quiet they are. No noise/hiss whatsoever.

Here is a pic of what I've got.



Bret608

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Re: OC75 G2R7 transistors
« Reply #3 on: September 07, 2017, 07:25:50 AM »
Cool! I think those are Phillips--I checked last night and the Phillips one I have is marked in a similar way. It says "C29" or something like that.

Which MkII variant did you try them in? With that level of leakage, I would think they'd work better in the earlier MkII/Supa Fuzz version with the 10K/47k rather than 100k/100k bias setup. Also, if you need higher gain let me suggest LIC Pedals for matched sets. He has a store on ebay and is nice to deal with.

szec

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Re: OC75 G2R7 transistors
« Reply #4 on: September 07, 2017, 08:37:57 AM »
OK, so it seems they are legit. I tested it with 100k/100k setup as that was what I already had. I am planing to build one with lower resistance values once I have some time (I only need to finish my contract in UK and move my house and family to continental Europe - that shouldn't be too difficult  ::) ) Unfortunately, LIC is based in US so it is bit too pricey for me to buy from his store.