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Geronimo . . . nium . . . um . . . um

Lucifer wrote:Hi Dr N

Have you checked that you didn't misread the label and bought geraniums instead ?

How else to get that elusive bloom?

Seems appropriate to post what's troubling me here.

It's been a while I'm unsuccessfully trying to build a TB MK I..Obviously biasing those trannies can be tough on this layout (trying it with the trimpot method) but I'm starting to worry my germanium transistors could be the ones to blame.
I bought about 15 of them,different types : CV7004s,AC125s,OC71s,Mullard OC76s.

I used the Geofex test to measure them and most of the CV7004 tested good on hfe and leakage,one OC71 and one AC125 were in range while all the other AC125 and Mullards were junk-(so much for NOS mojo-jojo crap!).
Anyway, has someone used any of these transistor types with success?Should I give the "faulty" ones a chance too?

I just can't seem to make the damn thing sound like I imagine it should..Thanks!

You need box of transistors to find proper trio for MKI. This circuit is really bitch to bias.
I saw builded MKI with AC125, OC71, OC76, CV7003. Part number is not so important...

beedotman wrote:You need box of transistors to find proper trio for MKI. This circuit is really bitch to bias.
I saw builded MKI with AC125, OC71, OC76, CV7003. Part number is not so important...

Thanks, I think it's coming to my attention what a bias bitch this circuit is!

Since you're a lot more experienced I'd like to know your opinion on this one:I can get my hands on NOS,tested within specs,quality (Mullard,Newmarker etc) transistors of more appropriate types (OC44,OC84,OC82,NKT272,AC128,OC76) for such applications.
The seller seems very reputable but the average price I get is 7,5euros/tranny.You think it's worth it?
Buying bulk poses more of a risk for me since I might end up with empty hands, plus I only want to build 4-5 pedals using Ge transistors.
Cheers!

NKT272 are awesome for fuzz face, OC84 for tone benders and OC44 for treble boosters.
7,5EUR for single transistor is pretty high, but I paid more few times. If transistor is tested, and You really want NOS shit with good part number - go for it.
CV7355 are nice transistors for boosters and fuzz faces, usually pretty high gainers but with low leakage.
Small Bear also is selling selected pairs/trios for many types of fuzz. You can try them for beggining.

Yeah, if you're not very experienced with buying and testing germs, just pony up a few tested trios from Smallbear. If you try buying Germs on your own, you'll only yield a few usable ones out of a handful. Then even if they measure ok, they can still be noisy. The MKI isn't a hard circuit at all, you just need good transistors.

phibes wrote:Yeah, if you're not very experienced with buying and testing germs, just pony up a few tested trios from Smallbear. If you try buying Germs on your own, you'll only yield a few usable ones out of a handful. Then even if they measure ok, they can still be noisy. The MKI isn't a hard circuit at all, you just need good transistors.

I've built the Geofex test layout to test them but out of the batch of 15 I purchased no combination yielded satisfying results.
That's why I'm considering to buy those expensive,pre-tested NOS ones so I can have some quality ones to work with.
The tested pairs/trios from Small Bear aren't any cheaper than the other guy but if I understand well they are guaranteed to work in the stock circuit with no biasing?
In any case if any of you have any spare good ones I'd much prefer to buy them from you rather than give my money to SmallBear or whoever else..

Ah yeah, not yielding any sets out of the batch is norm. Sometimes you'll hit a home run, sometimes you'll hit your hand with a hammer.

Which seller is pre testing? Sometimes pre testing is even dodgy. You don't know how they're testing them. The biggest issue with that is room temperature that they measure in. I've been burned on that one. Then there's the noisy/hissy factor. Happens with all kinds. I've had to junk 81D's for being too hissy.

Smallbear might not be cheaper but in the end, it's just the most practical route. I see he's got MKI sets now so yeah, that'll save you the hassle of swapping resistors and shit. I've never had to mess with any circuit changes with the MKI though. Give it some good transistors and it'll play nice. You could always buy two sets to get the best combo too.

Thanks for the advice!
I'll probably get the SmallBear set and add a few untested ones in the bag, maybe I get luckier this time.

The seller is Langrex from the UK.

Today I received 50 pcs of 104NU71 npns.
After making a first measurment the most common HFE is 50-70.But the leakage i measured is pretty high at 500-900 ua !!
Tomorrow i will make a new more accurate measurement with a 9 volt battery.
The adapter today was at 9.8volts .Also I will be at 22-25 Celcius room temp because today i was at almost 30 !
My God what a high measures difference when changing the room temp !

Anyone using 104NU71 trannies ?