Cornish TB-83 Treble Booster?

nickbungus · January 14, 2019, 03:21:32 PM

Thanks Tom, I'm picking it up tomorrow. I'll reassess when I have it.

nickbungus · January 22, 2019, 09:15:05 AM

Ok - So I ended up buying it and I'm on a soak it overnight (acetone), scalpel, repeat system but its slow going. I am yet to excavate a component. I have however got a clean view of the copper/solder bottom.

Now I know its a RangeMaster clone with an NPN tranny in it (probably silicon) and I also know that Greg Covington probably cloned it and in another post I traced that, so heres the schematic of the trace:

So we determined there are some unnecessary components that seem to be antipop resistors and power filtering, so bearing that in mind I think the layout is something like this.

There is that dirty big diode that I have left off that you can see on the previous images. I'm pretty sure I am wasting my time really as I doubt I will find anything I wasn't expecting but that need to know has consumed me!

Was wondering if anyone thinks I've got the layout right as Tom said, it helps to know where things are before I start mining?

nickbungus · January 27, 2019, 05:03:30 PM

Can someone please tell me the purpose of r10 is on the schematic above and tell me what difference a larger value would make and a lower one?

Thanks guys

sopapo · January 28, 2019, 04:42:45 PM

its the same schematic that the greg fryer treble booster, in that its a silicon rangemaster slight modified with two rc filter at the output to smoothering a little, the 150k and 47 form a rc for 20 hz, and in the case of greg fryer there is another rc of 4,7n and 560r to filter very high freq its look like your schematic is lacking the resistor, witout it the 4,7 cap has no sens I think....
the 1m resistor its obviously a pull down, the same at the input, the two electros in parallel are to filter( its look like he dont have another cap )

....c5 it will be the canonical 1n...
Good job on taking the time and effort to deggooping a tb83, I have looking since forever to build me one and I am just about to built a greg fryer on vero, but I suspect that the vero will serve me equally.... I will wait to know your findings... Which tranny it will use?? i bet the bc239...

Lookin forward to hear you Nick!!!
Thnks for your time

ElectricDruid · January 28, 2019, 06:27:03 PM

Quote from: nickbungus on January 27, 2019, 05:03:30 PM
Can someone please tell me the purpose of r10 is on the schematic above and tell me what difference a larger value would make and a lower one?

It doesn't make much sense, since it's in parallel with R9. The resulting value is what you get from the familiar "parallel resistors" calculation, and it might as well be a single resistor.

That assumes the diagram is correct. When I see things like that, I think "mistake!". In that case, I'd first assume that the lower end of R10 actually connects to the upper end of R9, in which case R10/C7 make a LPF to trim highs. But that gives 225Hz, which is a bit ridiculous. Back to square one.
So... perhaps it's the lower end C7 which goes to the upper end of R9, in which case it's a HPF at 225Hz. That'd trim some mains hums, and also tend to emphasise the "treble booster" sound by backing off the fundamental of the lower notes of the guitar.

That's my take on it. There are three possible situations there. You'll have to pick the one you like best!

HTH,
Tom

nickbungus · January 29, 2019, 04:42:52 AM

Sorry - just to clear something up, the Cornish TB-83 does NOT have the 1M(R9) in parallel. I think this was a Covington mod in an attempt to reduce switch popping (same as R4).

sopapo · January 29, 2019, 12:56:00 PM

it would be great if we can get a grasp on how cornish does the wiring, how he does the wiring layout, he seem to use shielded cable in all the conections inside his pedals, I wonder too if he does the star ground thing.
Nick, the unit do you have is the one without pot isnt??
I understand that in the case of the cornish unit, r10 with c6 form a highpass at 23 hz....

Ben N · January 29, 2019, 01:02:54 PM

What a BIG box for such a little circuit!

nickbungus · January 30, 2019, 06:22:19 AM

If you look at the schematic for the Covington and then look at TB-83 layout, the part numbers that I've labelled in overlay match. I did get R10 and C7 the wrong way round but that doesnt change anything.

The cabling isnt shielded and I dont understand star grounding but my overlay should tell you.

nickbungus · January 30, 2019, 06:23:23 AM

Quote from: Ben N on January 29, 2019, 01:02:54 PM
What a BIG box for such a little circuit!

Its because its battery only so most of the enclosure is jacks and battery space

sopapo · January 30, 2019, 09:33:14 AM

Thanks Nick for all, so in the tb83 at the output we only have c6, c7 and r10 itsnt??.
Are you going to degoop the side of the component?? To check values and tranny id?? Are you going to post more pics of it??
Best regards

Frabbio · February 10, 2019, 07:59:12 AM

A good way to remove epoxy is by using the appropriate solvents, acetone is not very effective. You should give a try with DMSO (Dimethyl sulfoxide,use appropriate precautions, butyl gloves and avoiding inhaling it) and a heat gun.
The best way I know for effectively removing cured epoxy is using DMSO in a mix with pyridine, but it will also destroy plastic packages.

Resynthesis · February 11, 2019, 05:13:59 AM

Quote from: Frabbio on February 10, 2019, 07:59:12 AM
A good way to remove epoxy is by using the appropriate solvents, acetone is not very effective. You should give a try with DMSO (Dimethyl sulfoxide,use appropriate precautions, butyl gloves and avoiding inhaling it) and a heat gun.
The best way I know for effectively removing cured epoxy is using DMSO in a mix with pyridine, but it will also destroy plastic packages.

Ah, interesting. Mrs Resynthesis uses DMSO at work, hmmm

nickbungus · February 11, 2019, 08:02:59 AM

Thanks Guys

I managed to scrape it all of going slowly using acetone and alcohol. I used acetone to soften it up and the alcohol on myself (mmm Heineken!)

I'm just testing a few things but I will be posting my findings very soon!

ElectricDruid · February 12, 2019, 04:06:04 PM

Quote from: Resynthesis on February 11, 2019, 05:13:59 AM
Mrs Resynthesis uses DMSO at work, hmmm

Well, whatever it takes to get you through till five o'clock, I suppose! I've never heard of it, but I'm sure it beats a couple of beers at lunchtime.

sopapo · February 14, 2019, 04:58:32 PM

Greg fryer in his blog, give us a clue about the cornish one in his "tri-trebleboost" proyect https://fryerguitars.wordpress.com/pedals-tech/
Check this!!

nickbungus · February 16, 2019, 06:59:45 AM

Seems similar to what I've got. I was questioning the 47k resistor from output to ground on my Cornish but that seems to confirm it.

I've got much bigger values for the electrolytic caps. I've no markings but the power filter one measures 137uf and the other one measures 87.

bool · February 16, 2019, 10:37:20 AM

A bad 150uf and a bad 100uf?
A good 120uf and a very good 68uf?
An excessively "good" 100uf and a fair 82uf?

nickbungus · February 16, 2019, 12:44:31 PM

I've built a clone and used a 150uf and a 100uf. Sounded the same.

nickbungus · February 16, 2019, 01:47:32 PM

Oh. And the tranny is a bc549c but to be honest I was trying others and it didn't make much difference.

I keep meaning to draw it all up but I've been busy at work.

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Cornish TB-83 Treble Booster?