"Latest RM Mods Brief"

[formerMember1]

hi,
sorry petemoore, had to use part of your title. :wink:

I built a rangemaster clone.  I used the geofx site for most of my reference and used an OC44 transistor from smallbear.  I used a 10k pot.
I use a hendrix strat clone i built. So for me i wanted a little more oomph from the RM.  I tried increasing the input cap, like everybody does for strat guitars, and i thought it lost the magic that the RM has.  It decreased the sparkle or something.  So instead I have been adding a resistor in series with the first lug of the pot.  I first tried a 8.2k resistor and liked it, but it was a little too heavey.  I then went down to a 4k resistor(actually (2) 2k resistors in series) and liked it but it was still too close to the stock 10K value.  Then i added another 2k resistor in series and got 16K.  I really really like the pedal with the strat now.  It still has the high end sparkle and is thicker sounding.  I always use the tone controls on the strat to change the tone.  I didn't care for the added tone control to the pedal itself.  It lost too much gain. And i would rather be able to control the sound from the guitar,(no channel switching for me) The pedal still loses a little gain when you roll off some treble via the guitar, but not much of a noticeable difference.
I think the pot now goes from 6K to 16K.  I have to disconnect it and test with the DMM.  That is fine with me, cuz i never used/use the boost pot turned all the way down anyway.
Just wanted to post this in case somebody else used a strat and didn't like increasing the caps for more oomph.

Oh yeah, The transistor measured 73 as it's true hfe.(from smallbear)  I have it biased at 7.00volts exactly.  I tried other transistors but think the OC44 is the best.  I never tried the OC71, but i hear it is very similar to the OC44.  

I didn't try the pedal with a humbucker guitar yet.
hope i at least helped someone, and contributed something useful to the forum, instead of just taking info.

thanks,
:wink:

PS:What did you modify on your Rangemaster to match your needs?

[formerMember1]

Anyone try a higher hfe OC44 transistor than 73?  I was wondering what would happen if i used say a 100hfe OC44 instead of my 73 hfe.  
Would it actually give it more gain or would it not change much since the transistor will sound the same when it is biased to 7.00volts

thanks :wink:

[AL]

Just out of curiosity - what amp are you running through?

AL

[petemoore]

Use on dude... .
 If there's a line you feel you crossed, you probably just felt that for a second   !
 'That's the way it is'.
  :arrow: I like reading mods briefs.

[formerMember1]

PETEMOORE:


well you are the one who got the pedal to sound so rad.  You advised me to add a resistor in series with the top lug between the V+ supply in another thread i started,  it worked great.  Better than changing caps.  :wink:

thanks

[petemoore]

Did I?
  :oops:
 Glad I could help...lol !
 'That pot's value is the Q2 collector resistors value', something like that is what I remember typeing 'IIRC".
 AFAI'm concerned, some of those Rangemaster resistor values might best betweeked out after a transistor is chosen. I haven't yet got concerned enough to type from experience.
 I did sketch up a rangemaster schem, whipped out the raw board, figured out the socket is where the electrocap goes, installed another one [see recent socket use post in the other thread weve been posting on], fired it up. So maybe I play, maybe I tweek...got tomorrow off !!

[formerMember1]

Petemoore said:
AFAI'm concerned, some of those Rangemaster resistor values might best betweeked out after a transistor is chosen.

Cuz i thought those RM pedals are supposed to sound better with a humbucker guitar then a single coil guitar.

The guitar sounds fine through other amps.
I even tried setting the bias at other voltages instead of 7.00volts

I do like 7.00volts better than anyother bias settings though... :wink:

anybody have same delemma? :cry:

[Fret Wire]

the amp is a Kay. sounds awesome though. It sounds more like a marshall than a fender amp. Since it is so old and worn, the speaker sounds really good because it vibrates really nice adding a nice speaker distortion to the mix. I am contemplating replacing the tubes. I think i will replace them when they conk out. Same as my guitar strings, i think they sound better after about 3-4 days of playing. I don't like the sound of new strings. I use curt mangan 9 gauge. they sound pretty close to ernies balls.

Maybe the amp's voicing and the humbucker's freq response are just not getting along. How does the amp sound with just the wolfgang? That's an older amp, and if the electro's are dying, the HB's could be pushing it just enough to fart out with the RM. Same with bad tubes, or a speaker ready to die. Btw, that amp runs the tubes off AC, so make sure it's up to spec, or you can end up with 120v AC live on the chassis.

[formerMember1]

yeah it still got one of those 2 prong cords.

I did notice that w/ the 2 prong AC  cord if i plug that cord in backwards in an outlet, you get shocked really bad, when touching say the guitar and a metal pedal, or even the chassis,  So i switch cord around and it doesn't shock, I guess i should switch it to a proper 3 prong grounded cord anyway.

I didn't complete my order to smallbear yet,(i was gonna place it today) i guess i could get a cord off him to wire into the amp.

I have to go reread geofx info about doing this,

thanks :wink:

[Fret Wire]

This should be another thread, but at the minimum you should probably replace the following in your amp.

C1A/C1B/C1C: multi-section electrolytic, all sections 40uf @150v.
R3: 150 ohm 5 watt -  replace with same value, 5 or 10 watt.
R11: 150 ohm 1 watt - replace with same value 2 watt carbon or metal film.
Three prong plug.
https://schematicheavencom.secure.powweb.com/bargainbin/kay703_2nd.pdf
Alot of those little amps without power transformers sound good, but they can kill you quicker than shit if they are not fully up to snuff.

Actually, for safety's sake and peace of mind, it's better to replace every cap and resistor in those amps. They have so few parts, none of which contribute to any "mojo" tone wise. Other than the two resistors mentioned above, the rest can be replaced with 1/2 watt carbon comp, carbon film, or metal film. The multi-section electro would be replaced by 3 individual electro caps, the rest of the caps can be replaced with 400v orange drops or Mallory 150 type caps.

[formerMember1]

thanks, I will try that, I am aware of lethal volts :wink:

[Fret Wire]

Awareness of lethal voltage is one thing, but...........

I did notice that w/ the 2 prong AC cord if i plug that cord in backwards in an outlet, you get shocked really bad, when touching say the guitar and a metal pedal, or even the chassis, So i switch cord around and it doesn't shock, I guess i should switch it to a proper 3 prong grounded cord anyway

that sure doesn't sound like you have enough respect for lethal voltage!

The fact that your still using this amp proves that. And I'm sure it didn't start doing this just yesturday. These types of amps are not like what you're used to. They don't have power transformers. When they fail, you can get a full 120v live on the chassis. There's a popular nickname for these type of amps: "Death Amps"!

Do your self a favor: cut the end of the power cord off and stick it in the closet until it is properly serviced, or it will sooner or later teach you a lesson in respect that your surviving family members will talk about for sometime. :wink:

[formerMember1]

ohh thanks for warning me

[formerMember1]

One other thing:

The fact that your still using this amp proves that. And I'm sure it didn't start doing this just yesturday. These types of amps are not like what you're used to. They don't have power transformers. When they fail, you can get a full 120v live on the chassis. There's a popular nickname for these type of amps: "Death Amps"!

Do your self a favor: cut the end of the power cord off and stick it in the closet until it is properly serviced, or it will sooner or later teach you a lesson in respect that your surviving family members will talk about for sometime.

when you say "When they fail" Do you mean a tube blowing, a cap dying, etc...? Wouldn't i only get electricuted from touching the chassis then?  

I was going to carefully remove all the parts from the chassis, without unsoldering anything, and build  a clone of it in the existing chassis, using the parts removed as a guide along with the schematic, Replace speaker with a new one, new tubes, new transformers , replace  AC cord, etc...
(Virutally build a clone of the amp from scratch.)

So that  i could learn more about amp building, Because i want to build a handwired Marshall 20 watt head(like the ones marshall is reissuing currently) And i figured i might as well start with this amp, since it has few parts, and i have one in front of me to compare it too. It is also cheap, and that way i wont ruin a 1,000 dollars worth of parts for a Marshall head.

Will the amp then be safer?  Or should i just stick it out on the road  with thursdays garbage? :roll:

Thanks FRETWIRE :wink:

[Fret Wire]

when you say "When they fail" Do you mean a tube blowing, a cap dying, etc...? Wouldn't i only get electricuted from touching the chassis then?

You could get zapped through your axe. And your caps have been dying for years already. If one goes open...it's bad.

I was going to carefully remove all the parts from the chassis, without unsoldering anything, and build a clone of it in the existing chassis, using the parts removed as a guide along with the schematic, Replace speaker with a new one, new tubes, new transformers , replace AC cord, etc...
(Virutally build a clone of the amp from scratch.)

You can't do it that way. All the components are directly soldered to the pot lugs, tube socket lugs, and solder lug strips riveted to the chassis.

The easiest way to service that amp is to go over the schematic, check the values against your amp, take pics of the chassis and components, and order the parts. Then, you replace one component at a time in the same place it originally was. That guarantees you'll get everything hooked up right. You won't learn alot, but the amp will be safe and give good service for years. Plus, never run one of these amps on an outlet that you haven't personally checked with an outlet tester. As RG always advises, adding an isolation transformer is extra insurance that will really make the amp safer.  To replace the speaker, you have to remove the ot transformer, which is riveted to the speaker. Weber's replacement speakers have the mounting pads on their speaker frames for the transformer.

That amp is easy and cheap to overhaul, and if done right, will be perfectly safe to use. You'll still gain some experience that will be of value later.

But, until it's serviced, put it up ....it's waiting to kill you.

[Peter Snowberg]

when you say "When they fail" Do you mean a tube blowing, a cap dying, etc...? Wouldn't i only get electricuted from touching the chassis then?

The trouble with "Death Amps" is that the bridge and your strings **** ARE PART OF THE CHASSIS!!!! ****

You CAN make a death amp safe by installing an isolation transformer (120V -> 120V), and then connecting the *OLD* neutral line to the ground of your new three prong plug.

Power travels the path of least resistance. When the heaters are powered up, the main power flow in the amp is there keeping those things hot. When ONE heater fails, the series heater topology causes the rest to fail and now you have serious potential for death.

It comes down to how conductive are your shoes and how sweaty are your feet? Don't think for a moment that shoe rubber is a good insulator. It's not.


I'll second Fret Wire, rebuild the amp and add an isolation transformer. You'll probably end up with a cool little amp and a bunch of great experience.

....until that time .....snip the plug off the power cord at least and put the thing aside until you have the isolation transformer and three prong plug.

They're called "Death Amps" for a really good reason.

[Fret Wire]

Good post Pete, a hellava lot more clear and consisely put than mine.

Sorry if we sound like we're ragging on you Ritchie, we're not. It's just that when you posted about being shocked by an amp I knew didn't have a pt, it's only being responsible to give you fair warning. After all, you want to play like Jimi....... not die for rock n' roll like him.

Funny thing is, a lot of those amps were UL approved when they came out. :shock: Just like all the old "All American Five" type ckt radios. I shudder to think some of those might still be in use, unserviced, in a kitchen (wet) area. Nothing but a bakelite knob standing between the user and death.

[Peter Snowberg]

Thanks Fret Wire. I thought your information and clarity was top notch. Thanks for the schematic link too!!!! I love it when that kind of info gets presented in an answer!

Thanks for raising a mini-ruckus on this issue. "It's better to be safe than to be cut into thousands of pieces and set aflame."

Ritchie, neither of us wants to sound like we're ragging on you at all. It's just that this is really important and really dangerous. A little work and you'll have a safe, new amp.

Best of luck with your future amp projects! Be sure to read up at http://www.ax84.com and http://www.18watt.com . Check out Doug Hammond's Firefly at AX84!

[formerMember1]

RAGGING?, No Way,  I highly appreciate the help.  Until today, i never knew about "death amps".  :?

Now i do.  

I will definitly take the advice of not playing it until i "safety fix it" :wink:

that is a better idea to take a picture of it and replace one part at a time.

I already replaced the 3 filter caps, a long time back(possibly a year).  Yeah I am thankful for the schematic, it has one stapled to the cabinet, but it is hard to read,(all yellowed)  The schematic you posted, printed out nice and Big  and Easy to read.  

I understand that the tube sockets etc... are riveted to the chassis, I was gonna drill them off and re rivot new parts in,  If i was going to replace all the caps, resistors, etc.. I thought i might as well replace the sockets, (they are in really bad shape) and everything else.  I was actually thinking about building a clone of the amp first, then modifying it different ways, to learn some things.  Kinda like Eddie did to his old Gibson guitar, then he built his own guitar after he learnerd off (and ruined :lol: ) the Gibson.

I am gonna do some reading on those links you posted, and i am probably going to join some amp building forum.(probably hoffmans :?: )

thanks again FretWire and Peter Snowberg the heads up was appreciated.

I think buying this amp for ten bucks, and learning off of it was/is a good investment,   :wink:

Now if i could only learn enough to build a  Marshall Plexi era amp.  i think the prices on those new handwired ones are ridiculous!


Hey talk about a thread that stemmed off of another thread.(highjacking)
:oops:

[petemoore]

It's easy to get used to 'I can do anything with 9v' approach, and thats not bad, a burnt cap pot or OA can be replaced and messed with again.
 It's also easy to see how these circuits are similar in many ways to tube circuits.
 Diving into a tube amp like you would a circuit board with a battery clip hanging off of it is strongly recommended Against.
 Discharging large caps is a good idea if your'e working right next to them or not.