help re: java boost clone

[stm]

Thanks Doug_h and Fret Wire. Nice article. Mmmhhh, I wonder if there's a way to obtain these results with a MOSFET or JFET instead...

[dansamp]

ok I completed my vero board wiring
using the latest edition and it doesn't work!!!!! :evil:
i biased the transistor using the geofex recommendations
7.0 volts from collector to ground
i am subbing an NTE 100 withe an hfe of 40
and i get now sound
i pulled out the transistor and the transistor socket is hot to the touch



what gives??? :cry:


any ideas      

[bryantbr]

The schematic posted here by Kusi didn't match the actual java boost I had in my possession.  Very close, but not exact.  But hey, everyone here will tell you "it's just a rangemaster with trim pots, tone control, cap switching."  I have the schematic matching the board now in ExpressPCB.  Now I just have to clean up the traces and I'll be ready to make a board.  May breadboard it first.

[dansamp]

never mind!!! :oops:
it helps if you drill out ALL the breaks in the strips!!!!


i forgot to drill the trace to the right of the emitter !!!!!
it is 10:30 p.m. and i am running it through my narrow panel pro clone
and it sounds pretty cool
   
have to go to bed
i will try it out some more tomorrow
so far it sounds great
i have to find a suitable transistor
one that has a higher gain
also at this volume the tone knobw doesn't do much
but i will check it out again after work tomorrow eve


for now it sounds better than my rangemaster clone  :wink:  :wink:

[petemoore]

You get enough transistors, you probly dont' need all them resistors as pots.
 The adjustable ones, I make larger''ish value, then parallel on there enough to adjust or clip a pot on to find the value that...well I end up with a 'piggybacked' resistor on the board, of X value [has to be smaller than the one you don't take out]...to set that part of the bias...not so bad, I have this way of just tacking one end, then pressing the body and adding solder to the other end and heating real good, then come back to the side I used to hold the darn thing...so I could get it started on there without having 5 hands or twisting it 'just 'right...
 For the serious Rangemaster tweeker, ATBB, and OTBB, and [1 ge booster types apply]...I built Ge booster testboard, and it had either sockets or trimpots for any resistors I though I'd might wanna be tweekin' on...basically if it was a PNP Ge i had, I could get bias on it [if it was worth a bean] and see how it sounds...preferring the bare circuit for the most part, maybe dudes' using a certain gain tranny and voicing it more or something.
 I do like the dudes in the 'old days' when these things first started coming out would [or try] ... get the best parts/pieces you can [try for good parts] and work with what you have 'till you achieve the best tone you can with the parts you were able to accumulate.

[dansamp]

so does it matter if the hfe is below 70 as long as it is properly biased??
and on that note do i still check the bias going from collector to ground ??
does this change since we are using a PNP transistor with negative ground and the original rangemaster was a positive ground PNP? :?

[petemoore]

RUnning PNP's neg. gnd. ... [  ] I don't know ...
 I'd suggest considering setting the transistor, PNP, up with a Pos Gnd. and see if that works better. Posters report having problems 'PNP negativing', I forget the tech reasons offered for them, often these threads were settled with a Pos Gnd setup re better' performance.
 I forget what the suggestions were for PNP NEG, something like a diode to hold bias...reading occasional reports on how it got to working as good as using original neg. gnd. scheme ... perhaps there's a surefire way to do it, I don't know it though.
 NPN Ge's are different sounding too somehow, again daft IIRC< something about the construction is different...but I've gotten these to work with Neg. Gnd.
 Rangemaster is a finicky circuit, re-bias[s should be performed with each transistor used. Transistor temperature may cause bias drift.
 To be contrary, I suggest handling the transistor to Raise the internal temperature, then perform the interview in the circuit over the cooling time to see if a fixed bias can 'withstand' temperature fluctuations...listening for, and trying to adjust for, temperature sensative transistor gain variations...trying to keep that transistor running as optimally as possible throughout the 'normal' range of temperatures it will most likely be run at....of course it is rather cold in the basement where I performed these test...

[dansamp]

yeah what  you said  :?

since this is a java boost clone and the circuit is using a PNP transistor
and it is negative ground
how do i check the bias now

or to put it another way
what should my voltages read at the transistor E. B. C. ?
should i use the values posted earlier on this thread
B: 8.0v.
E: 8.15v.
C: 2.64v.
and are these readings with all legs of the transistor in the socket
( as opposed to the GEO notes where the bias is checked with measuring the collector voltage to ground)  :wink:

i am also going to try a NTE 158 that has an hfe of 90

but i am at work so it will have to wait 'till tonight

[petemoore]

Geo article on RM...for best bias correction reads I know of...
 The collector is supposed to be about 7/9ths of the PS., or 7v if using a 9v Power source.
 What does your PS measure when connected to the circuit. Always necessary when looking at V's to know supply V, 7/9ths is close to the rail on RM's...
 Looks like a bias issue though...resistances from 'here' to there'...'can' be checked sort of while in circuit...to see if they actually Are connected correctly and the right value, IF there's no other current path, OR if you do math or pull one end up for measureing the resistance through Only that path...through the resistor.

[dansamp]

ok i tried the NTE 158 and it sounds great
the voltages are dead on also

but again the tone knob does nothing


could one of you experienced E.E. 's check out the layout for me and let me know if it's me or perhaps the layout is wrong??


thanks a lot for any help  

[modmod]

Kusi,
I used your schem in PCB Express and I still can't get all the pins/leads to match up.  Take a look at the pics and see what you think.  There is a trace under the input cap socket connecting the top lead of C2 to the top lead of C1.  

It's a bit hard to read the pcd..... it's double side pcb ? did u flip the bottom side picture ? i don't see "a trace under the input cap socket connecting the top lead of C2 to the top lead of C1", am i right ? thx

[Torchy]

Sorry, wire link missing from tone pot to collector. Corrected now.
here

[tungngruv]

Torchy, you are correct. I put in the missing jumper and now it's 100% functional! Thanks!!! Very cool!! Here are a couple things I discovered:

-100K trim gets the sound going, 10K trim fine tunes the gain. I know your supposed to measure the volts on the collecter BUT... I found that I like it more when I fine tune the trimmers by ear, really. You can get subtle break up to really fuzzy. Sometimes ears are better than multi-meters?

-the tone control is subtle but there. Building this from Torchys layout: counter clockwise for high end, clockwise to take some of the "presence". Thanks again Torchy.

[dubs]

I made a RM clone for someone with a toggle input cap switch.
I A/B against a Keeley Java boost I had on hand thru a matchless spitfire.
Both had oc44, and the clone was much smoother and had more punch, the java boost was more fuzzy and overdrives more quickly.
Having tried both cv7003 and oc44 java boosts, I have to say I don't like the sound of them,  but the clone sounds great.
I don;t know whether the addition of a tone pot puts a load on the signal and affects the tone, or whether Keeleys tweaked the trimpots for more distortion.