Got my Meteor running.......

[MartyMart]

..... head out on the highway (89)  !!
.... yeah "Lame" ... I know

Went back to this after a year away from a "messy" layout and rebuilt it with a whole new Q4/Q5 section.
I originaly had nothing at all, but now have the most fantastic grinding distortion   BUT ....
It's squealing like a pig and is a nice oscillator !

Modifications :
Tried removing the 51p bright cap
Kept leads as short as possible
Added a 47n input cap and 18k input r before Q1
Changed the 220uf at Q2 to a 22uf
Tried an MPF102 at Q1
All drains bias at around 4.5 - 5.2 v

All this has improved it a little, but gain past 1/4 pot travel brings the squealing right back !
Any ideas ?
Shield the I/O cable ??
Is Q4 having similar trouble to the ROG Thunder Chief woes ..?
It's so close to being an amazing pedal blows Dr Boogie out of the water ! 
Thanks,
Marty ...... "stumped" !

[tcobretti]

Is it as "metal" as a Dr Boogie?

[pbrommer]

I opened mine up, so maybe I can point you in a few directions. I made some changes after I got the schematic.

I have all J201s in there. I had issues biasing Q5, but I found one that finally biased to 4.5Vish.
I have no input filter like you've put on there (47n/18k)
I have no C11 - I just realized that. Perhaps omit that?
Bright cap is switchable (100pf/500pf)
Try changing R9 to 10k?
Maybe change the NFB (R17) resistor to 100k?
Treble and Bass are 1M linear
C9 is a 22n capacitor
R6 is 4k7
C7a/C7b = one capacitor - 2n2
Nothing is shielded! (and the In/Out wires even cross!) It's quite quiet, just noise on high volume with single coils.

There's some of the changes I made. I'll stop back later tonight. Let me know what you find out.

[hairyandy]

Hey Marty,

I'm sure you know that Doug based the Meteor on a Trainwreck Express.  I don't really have anything to offer idea wise but the Express is supposed to be on the edge of instability which is part of the magic of these great amps.  I just recently bought a great Express clone made by a guy in California named Paul Ruby (http://www.paulamps.com) and it's completely over the top, definitely one of the best amps I have ever played.  I would maybe head over to the Amp Garage (http://ampgarage.com/forum/index.php) and search the Trainwreck forum for ways that people have tamed the high end on the Express and then try to apply it to the Meteor.  Just an idea...

Andy

[tcobretti]

BTW, in my fairly limited experience, a small cap across the collector and base of a transistor goes a long way toward killing oscillation, so you might try a 50-100pf cap across the drain and gate of your fets.  I'd try one fet at a time, then more than one if you can't cure it with one well placed cap. You'll lose some highs, but it'll help mirror the miller capacitances of the tubes from the original amp.

[9 volts]

I stuck to Doug's schematic but...i had alot of radio interference.  I fixed by adding a 22pf capacitor between the gate and drain of transistor two. Mine sounds great but I wish I could get a little more out of the bass middle and treble pots. Maybe I'll trey the above mods. I built it with 2n5457 then changed them all to j201's. What influence does the bright cap have?
I had not troubles with squeals.

[MartyMart]

Thanks for the replies chaps
That's given me some things to think about, it's absolutely worth chasing after a fix, the sounds
under my constant "howling" are VERY good 
It's a very high pitched squeal at mid gain, note drops in pitch to a motorboat near max gain &
lots of hiss ...
I also have a 1k r across the 9v line, dropping it to about 8.5v before the Q's and have a 220uf
over the power/ground.
47n and 18k are in series before Q1, just incase RF was getting in.
I'll have a "fiddle" and report back later .
MM,

[MartyMart]

FIXED  !!!  ( Thanks to all for the tips )

Probably had a tiny error across a trace, I cleaned up all the copper and removed every
bit of flux , also added a couple of 33pf caps over Q2/Q4 drain/gate and put back the Q2 220uf.
Reflowed most solder points also - just to be sure !
I removed the power limiting resistor, so 9.2v was hitting all the trimmers.
Tried several J201's at Q4, as this seemed to be drifting quite badly, every time I went to it with
the DMM the reading was different !! from 8v down to 2.5 - causing lots of splatty stuff to happen.
As with all these Jfet builds, simply relying on the drain trim pot for bias is a no no ! you need to
either mess with the source r's and cap's or keep trying lots of Fet;s till you find one within tolerance.

Thank you Doug, this is a superb sounding grinder with buckets of high harmonics - very "Brown" sound

Marty.

[petemoore]

..... head out on the highway
  I was about to bite on the setup and type this, but you got to it first !!!
  LoL !!! Glad you've figured how to set this thing up for yourself!
 

[MartyMart]

..... head out on the highway
  I was about to bite on the setup and type this, but you got to it first !!!
  LoL !!! Glad you've figured how to set this thing up for yourself!
 

Glad that made you smile
Added an mp3 in a new thread , but here it is again :
http://aronnelson.com/gallery/albums/album72/Meteor.mp3

What a wonderful "OTT" noise

MM,