high gain lee jackson gp 1000

[Meat&Beer]

PCB's are difficult to mod, I don't see that pre as a decent modding platform unless you know what you're doing, and you know what it is TO be done. Lots of room for error on those boards, lifted pads and whatnot...

Bypassing the clean channel could be done. Would it solve your problem? Well, that depends entirely on if what you've heard is fact. 700 bucks though? Not hardly.

You've got the schematic, just build a proper one for less than half the price of what you've been quoted to modify it.

[dorrisant]

10thtx probably has a schematic and layout already... Just waiting for Rune to divulge the last details.

Tony

[Cameron]

So you mean if I don't use the clean channel I could just nap out the wire driving it through the main PCB and problem could be solved? Kind of don't think that would work as planned but....tempting.
No don't use the clean channel, and it isn't very good either, of course If I wanted a good clean there are a lot of suggestions for shaping that one out too.

Yes buzz/fizz as the note decays, most prominent on the low E string while palm muting, but also present at the other strings as you let them ring out.

Edit: No the buzz is present without the clippers too, but not as prominent.

The clean is the front end of the gain...so that wont work. Even if you could ....its the grounding thats the problem. You can try to filter it out of the ground by putting a cap from ground to the casing ground...you have to fish around tho... get the pre to make that buzz with that low E like you said.......then put a cap from circuit board ground to casing ground...start with the first set cathode resistors and caps ......be careful if you do this with it live/on. Use a clip lead ..clipped to the casing where its grounded.. ....clip the other end to a .1 cap and touch the cap to different ....!!!grounds!!! on the circuit board... You will hear it change or go away when you are in the right spot.... thats the problem area. This is one of the things I do to find problems like this...It almost always works..... and its not a bad thing to filter out your grounds as well as the power sometimes too.

[Cameron]

So you mean if I don't use the clean channel I could just nap out the wire driving it through the main PCB and problem could be solved? Kind of don't think that would work as planned but....tempting.
No don't use the clean channel, and it isn't very good either, of course If I wanted a good clean there are a lot of suggestions for shaping that one out too.

Yes buzz/fizz as the note decays, most prominent on the low E string while palm muting, but also present at the other strings as you let them ring out.

Edit: No the buzz is present without the clippers too, but not as prominent.

Also... where this mod for the clippers is grounded and other things that go with the mod ...could also be the problem. Why don't you tell us more about this mod you have in there ..and some pics might help also.

[Rune]

Tech said it is a design flaw where the traces are too close and pushing more voltage makes it worse. Now as I said the only thing Ive tried to ground that way is the grids on the input tube, but that didn't work, at least not hearable.

So test grounding every PCB ground to main ground on the chassis with a small blocking capicitor? Well, could work, at least it could block some of the signal feedbacking the wrong way. (If that's the problem).

Mods include rising the caps on cathode 2 and 3 as well as rising caps on output stages and asymmetrical clipping on second tube. (adjusted with 10k pot instead of resistor). Also we've raised the mid pot from 10 to 50. C9 could be put to mesa boogie value instead of rising C3 if you like. It dose somewhat the same thing. We've also added a mesa style EQ at the end of the circuit for shaping distortion and are working on an extra lamp for that. Bit this last one is not a Bodom mod. Also tried diodes on all the inout cathodes just to test it, but isn't for Bodom either.
Also adjusted some bass and mid caps as gorhrut described early in the thread.
One mod hasn't been tested is to route the disortion stage through the bass pot giving it an extra distortionpot when pulled and a fixed bass value as constant when activated. Could also chabge c201 to marshall specs for more singing gain.

[Meat&Beer]

The clean is the front end of the gain...so that wont work. Even if you could ....its the grounding thats the problem.

Just to clarify on my end, yes the clean is the front end/V1. By saying "bypass", I guess I should've used a different word. "Disable", perhaps? One could do away with the switching/relay and related routing so it's a straight shot into the rest of the preamp circuit, thus disabling the clean function and eliminating the crosstalk. IF in fact, that's what is contributing to the problems. Like you're alluding to, Cameron, that might not even be the real issue.

Tony, that was a good one!

[Rune]

The relay setup is an ungrounded plug via two diodes, but the signal also goes through this preamp tube biasing pot (weird stuff). If you study the front and backside of the PCB what should I pull out of the circut including the blue relay switcher and how do I rewire so that the clean stays out of it?
This is where ny techincal understanding fails me a bit.

[Meat&Beer]

I can tell you exactly how to do this, and I'd be glad to do so. I'm not gonna do a paint by numbers for you, but this isn't terribly complicated so long as you can read little numbers and solder/desolder on PCB.

Remember that ebay auction you had with this? In the description it said the "winner" would get all assorted documentation, paperwork, schematics, notes, etc etc with all details of mods done and additional ones that could be, with the unit. I wanted to buy it, I wanted the unit and paperwork. You didn't let me. You denied my money for the fact of keeping secrets.

Now you're here, you want help from the people you've tried to belittle.

Post the Information for all to see.

"But wait, that's blackmail!!!" Well, it's more of a trade, as well as a chance for you to prove you're not a dick to all the viewers at home.

Now the Bodom forum techs failed to understand what needed to be done so there is no more protecting of mods and making money of it by anyone. And no more production.

Cute that you guys are discussing my auction and my knowledge on this forum.

So don't come teaching me about the GP-1000, I've dealt with the amp and it's possibilities for more than a decade now.

Edit: And I have a whole offical Bodom forum to proof that I know the mods Alexi had/have in his now retired GP-1000.

[Rune]

I found this site searching for a solution to the noise problem by searching for GP-1000 mods on google. Then I saw some of you discussing my emails to a potentional buyer of my second orginal unit. Yes I had two (on US power and one EU late 87 and 88 model). Since then I got additional emails from the tech who modified the Bodom/Stone/Sinergy units. Now while all this two techs showed up at the Bodom who did clone of the original unit. I got them info to improve and fix som errors on the fan made schematic floating around. They built me a unit with mods for 260 Euro. And while they built it I tested the mods my self on my 87. Not all the mods of course. And I left it with mods that didn't cause extra noise and decided to sell it. Which I did about 1 month ago.

I got pissed because you guys dismissed that I knew anything about making the unit high gain (more distortion).

Now sorry for that.
And the post I did on the page simply says it flat out what the mods are. I could say more values of course. Like 1uf< on C2, 1uf on C3, two or three low votage diodes on resistors at 2 tube. or if you want c9 to 4n7. 300n on c203 and 204 and 0.22 on C201.

Of course the emails from the tech would be even more vague (just said add a lot to C# and a little to C#) and I promised not to share his name directly. Some of the values are stated others are found trough testing for the pleasing ear.

Could draw a schematic with values I used but this pretty much does the same.

Of course could post the emails with blurred out names, but there is no more to see. Would have given less info to the buyer. Just qoutes from the tech and other amp gurus and their suggestions as well as a photoshopped schematic with where to change.

[Meat&Beer]

I don't really have time to read through this whole thread, but I certainly don't remember anyone dismissing your knowing how to make this higher gain. Whatever you've done/know how to do about that, there's probably more to be had, depending. For starters, one word: Bootstrapped.

Wait, are you talking about changing the values on the cathode of V1a? That'll more change the tonality than get you much more gain. And I believe that's already been mentioned.

What I was specifically wondering about, and I'm sure many others are, is the documentation you said would be included in the auction. I was one of those people you were corresponding with on ebay, Agormortis86. Just a little snippet here:

"I have a lot of other suggested mods from techs that have been modifying it for decades. But these will only be shared when the unit is bought and shipped. (pictures and schematic changes). "

Schematic changes, if you have that, it sure would be handy rather than asking us to memorize all the little changes that have been done. We think in terms of schematics here, that's why it's being so heavily harped upon. It's a "big picture" thing. To me, a schematic is a simplified layout. To some others, they may not be able to read a schematic and a paint by numbers layout is the only way they can build an amp. It's kind of dangerous that way, but that happens a lot.

Just post an updated schematic of what you have going on in there, for actual reals, and we can get on with modding the snot out of the thing.

[Rune]

Yes the V1a cathode change in C1 is just an ugrade Lee Jackson did in late 88 or 89. to 0.68uf and R1 to 820ohm. it's stock in about 2-300 out of 5000-10000 units. You get a little bit more tight tone. Not gainier, but it is stated so at the webside of the maker. C2 1uf or higher. C3 1uf. Thats about it on the input signal. Minor changes in tone stack, but nothing from the Bodom tech, just others like Larry from Larrys amplification (germany).

only big schematic chane except values are the diode inclution(s) in paralell to R204 (might include a uf cap as well for blocking unwanted frequencies to taste) and 10k trimpot instead of R204. Could draw one up, but is like 2am here, so another time, but surley it is as easy with part values when Ive included a part descrition picture of the whole amp and the original schematic.

[matt h]

(deleted)

[Meat&Beer]

So you don't even have an actual schematic with mods I take it? What do you have, just emails from techs? (Not trying to sound condescending here, just wondering what you're working with.)

I take it you can't actually read a schematic then? Like I said, I'm not going to go nuts following PCB traces in your pictures to make you a pretty cookie-cutter, but I'll tell you how my brain's telling me to do this. Start by looking at the schematic.

You see V1b? Cap C9 coming off the plate of that tube has your signal on it, going into the "distortion pull" switch. Disconnect this junction, and probably the whole switch itself if I'm looking at the photos correctly. Can you pull off the shield over the switching portion and post a photo? Can you straight up remove this portion or is it physically attached to the pot? (I'm sure it's attached, wishful thinking here.) If it's attached, it'd probably be easier to replace it with a regular no frills PCB mount pot. Or figure out how to parallel up the two positions so that pulled or pushed is the same outcome.

You want the loose end of C9 to go into lug 1 of the distortion pot, P2. Disconnect the relay from that lug, and attach signal from C9 here. (You may have to cut traces, pay attention to where they go in order to make this decision.)

The wiper of P100 (lug 2) gets disconnected from the relay, and re-routed to lug 1 of the Master(s). Gotta admit, this P100 and R17 look weird to me. Negative feedback? Some sort of adjustable grid leak type thing?

After this, I'd probably pull D5 and D6. But try the aforementioned before doing so and have it working first. Those diodes supply power to the relay, and once removed, your heater voltage may increase ever so slightly. My rationale here is I don't see why having an unused part should be supplied a voltage for any reason.

Also wait on removing the diodes until after, because, one thing at a time. No shotgunning. But after those two things are done, all that shit is now out of the circuit.

Take your time. I assume no responsibility should you choose to try this and wind up mucking it up. Good luck!

[Gorhrut]

i just wanted to clarify, rune.

did you replace r204 with a 10k trim or did you add a 10k trim in series?

if you added it in series you would decrease gain but you would get more distortion. its called a cold clipping stage.(in the pictures of jon's unit i posted earlier, you can clearly see that r204 is still there with a trimpot in series. cant tell if the bypass cap goes around both the resistor and trim or just the trim?)

if you replaced it with a 10k trimpot then as you adjusted the trimpot down you would get more gain(volume) which (could?) lead to more distortion.



also, it could be that if your problem is just with the low end maybe you increased the value of coupling capacitors too much? caused motorboating type effect? are those values and the values of c203 and c204 from the tech?

[Cameron]

You need to take this to a good tech...you are in over your head with what you want out of it.... its also something that needs to be in front of you to figure out...its not just a simple resistor change we can tell you.

Don't go chopping up the board ....you would be better off making a new board ...PTP or what ever ...using the schematic you have and the info you have ...its a very simple preamp ...very easy to make..easy to fix too (if this was in front of me I would have it running in an hour)... but.. not on a form thread. After you get that working ..you should learned enough to fix the old circuit board and put it back together.

You could also look at some of the dumble threads and look at some layout ideas if you build a new board...the circuit is a Fender clean with 2 gain stages switched in after..like the dumble circuit. It would help you to go read about higain preamps and the problems that go with adding gain.