Feel free to ask Myles

[soundbeing]

got it. thanks a bunch myles.

 

[martinaxman]

HI Myles. I'm a used to be EE who moved to digital and then systems due to market changes. Every so often I get the itch to get back into the electronics end. Probably a lot of company here. Anyway, I trained from the Navy manuals in analog and the core was tube theory through digital which at that time was very low density discreet circuits. Just the other day someone asked if I could repair amps. So it begins. What I'm wondering about is not exactly what you usually get asked. I'm more interested in what it would take to begin an outfit to do repairs and build circuits as you discuss here. Specifically, what kind of scope, specialized testing equipment would get me going. I remember Hitachi had a nice instrument years ago, Teks are always good, but I'm on a limited budget and have to try and keep it reasonable. I'm sadly poor on equipment other than a nice fluke digital mm and a couple of odds and ends like a frequency generator. I do miss this stuff and would love to get back into it.

 

Any insight would be appreciated. Thanks

 

martin

[myles_rose]

HI Myles. I'm a used to be EE who moved to digital and then systems due to market changes. Every so often I get the itch to get back into the electronics end. Probably a lot of company here. Anyway, I trained from the Navy manuals in analog and the core was tube theory through digital which at that time was very low density discreet circuits. Just the other day someone asked if I could repair amps. So it begins. What I'm wondering about is not exactly what you usually get asked. I'm more interested in what it would take to begin an outfit to do repairs and build circuits as you discuss here. Specifically, what kind of scope, specialized testing equipment would get me going. I remember Hitachi had a nice instrument years ago, Teks are always good, but I'm on a limited budget and have to try and keep it reasonable. I'm sadly poor on equipment other than a nice fluke digital mm and a couple of odds and ends like a frequency generator. I do miss this stuff and would love to get back into it.

 

Any insight would be appreciated. Thanks

 

martin

 

Martin,

 

This is hardly the venue to begin to scratch the surface and attempt to begin a response. I have over 500 pages on my GAB website that house or link to thousands of pages of documentation.

 

If you want to talk about this we would need to meet face to face .... for a few months ... just to get started.

 

[myles_rose]

Ebay

[Electric Biscuit]

Hi Myles,

 

Not sure if this is beyond your realm of knowledge, but I'm curious as to the possibility (or lack thereof) to convert old tube-based electronics (guitar amps, transistor radios, etc.) into a headphone amplifier. Is such a thing remotely feasible, and if so do you know of any helpful resources or reading materials?

 

Thanks

[Caevan O’Shite]

Myles, how're ya doin'?

[Sauce]

Hey Myles,

 

Hope you're doing well. Just wanted to run something by you to double check I have all my ducks in a row. If I wanted more headroom out of my '74 Deluxe Reverb I could throw a 5751 in v1 right? (I saw you recommended the JAN GE) And there'll be no loss of volume or output or whatever? And should I put one in v2 as well? Will the 5751's react any differently then the 12ax7's that're in there now to being hit with overdrive, distortion and fuzz pedals?

 

Also one of the vendors is offering "matched gain," "balanced triodes," and "matched pair" options. Do I need any of these?

[myles_rose]

Sorry for the slow reply. Did not get notified on this for some reason.

 

V1 is only for the normal channel and V2 is only the vibrato channel. You do not need to replace both if you do not use both channels. You will drop a bit in initial level but just bump the volume control by a half a number or so and you will be at the same level but with more headroom.

[Sauce]

Awesome, thanks so much Myles.

[myles_rose]

You are very welcome

[myles_rose]

I just posted links to this section on facebook and twitter

[Bluesape]

Happy Birthday Myles!

[myles_rose]

Thanks for the b'day wish

[Bluesape]

We have a thread in your honor.

[myles_rose]

Thank you very much for the b'day thread

[pinkjimiphoton]

hey myles,

gotta weird question for you...do you think i could successfully build a piezo tune-o-matic style bridge using piezo cable? i built a double neck, and would really dig having a piezo option on the 12 string neck...but MAN!! them piezo-equipped TOM's are pricey!!!

i was thinking if i bought a cheap TOM, and maybe routed just enough of a channel below the bridge saddles to snugly fit the piezo element, and then run a cable thru a hole on one side under the bridge humbucker and to a small preamp in the control cavity, i might be able to get away with it. do you think it would work?

or do you have any ideas of other ways to do this?

i've also thought about embedding a normal piezo element or two in some of the routs of the guitar, but figured it might be to "drony"...i appreciate the advice, bud! peace!!

 

EDIT: i found THESE doing a websearch earlier for piezo cable, do ya think one of them could be adapted somehow?

[bennyguitfiddle]

Hello Myles. I have a mesa boogie dc-2 studio caliber. Plays good to about 20 min. Then it starts killing the volume til you can't hear it. Let cool down same thing. Replaced power tubes no fix. Any help is appreciated. Thanks ben

[pinkjimiphoton]

hey ben, did you replace the driver tube when you replaced the power tubes? it's the preamp tube closest to the power tubes, usually a 12at7 or 12ax7. they get driven harder than the other preamp tubes, and if your amp starts sounding mushy, or dieing, it could be the problem. cheap fix if that's the problem, if not, i'd suspect a cold solder joint or an open winding in the output transformer...something is expanding and breaking contact when it heats up.

but i'd start with the driver tube...to test it, plug an extra tube or pilfered tube from another amp in the driver slot and see if the problem goes away. if it does, just replace it with whatever it's supposed to have in there, and that should take care of your problem hopefully.

we'll see what the man has to say!

peace

[bennyguitfiddle]

Thanks jimi I will give that a try

[myles_rose]

hey myles,

gotta weird question for you...do you think i could successfully build a piezo tune-o-matic style bridge using piezo cable? i built a double neck, and would really dig having a piezo option on the 12 string neck...but MAN!! them piezo-equipped TOM's are pricey!!!

i was thinking if i bought a cheap TOM, and maybe routed just enough of a channel below the bridge saddles to snugly fit the piezo element, and then run a cable thru a hole on one side under the bridge humbucker and to a small preamp in the control cavity, i might be able to get away with it. do you think it would work?

or do you have any ideas of other ways to do this?

i've also thought about embedding a normal piezo element or two in some of the routs of the guitar, but figured it might be to "drony"...i appreciate the advice, bud! peace!!

 

EDIT: i found THESE doing a websearch earlier for piezo cable, do ya think one of them could be adapted somehow?

 

I really do not know as I have not used these types of pickups from an install or wiring point of view.

 

[myles_rose]

Hello Myles. I have a mesa boogie dc-2 studio caliber. Plays good to about 20 min. Then it starts killing the volume til you can't hear it. Let cool down same thing. Replaced power tubes no fix. Any help is appreciated. Thanks ben

 

If it died totally and came back it would likely be a cold solder joint or broken etch etc.

 

In the case of slowly killing volume it sounds as if something in your poweer supply is dying. Time for the amp to see a bench and have voltages measured pre and post problem and which ones change.

 

[bennyguitfiddle]

The volume never dies completely. It just goes real low. And mushy.

[myles_rose]

Check voltages pre and post problem.

[pinkjimiphoton]

thanks myles, i ordered a couple to see what's what, if they work out i'll post back and let ya know!

[myles_rose]

Happy playing Jimi

[pinkjimiphoton]

back atcha myles!

[pinkjimiphoton]

hi myles, i gotta new problem i hope you can help me with...

 

recently i built a doubleneck sg style kit i got on evil bay. nice axe, believe it or not, plays great, sounds great...but it's got one problem that's got me stumped electronically.

 

each neck's electronics work fine, and i've got it well - balanced output/tone wise from neck to bridge on both necks, and even from neck to neck.

 

but when i put both necks on in parallel, that's when the prob is hitting....it's not a phasing issue, but i get a substantial volume drop...very noticeable, i'd say probably 3-6 db or so...enough where when you choose just one neck, it's about twice as loud.

 

i DO NOT remember my old gibson doing this...so i figure there's gotta be something i missed when i wired this puppy up.

 

do you have any idea what the problem is, and if so, how to fix it? i mean, i can live with it, but it's kinda annoying!!

 

thanks in advance,.

jimi

[myles_rose]

Jimi -

 

Meter the resistance of the pickups at the output jack in each position. Sounds as if when the necks are in parallel they are indeed in parallel and dropping the signal as the resistance is half of what it would or should be. Make sure it is at least 6-7k. If not, you can have a tech rewire them in series.

[pinkjimiphoton]

aha!! so in parallel it's loading it down more? dumb question, but could i add a small series resistance to accomplish the same thing without having to wire the necks themselves in series? it seems that wiring them in series is gonna defeat the purpose of having the necks parallel in the first place...i want to keep the controls independent if possible, wiring in series would mean if i shut one vol off completely, it would kill the whole guitar, correct? perhaps i may just have to live with it. as wired, it's more like an epiphone than a eds 1275...here's a pic of the wiring as it was supposed to be, stock:

 

http://i605.photobucket.com/albums/tt137/pinkjimiphoton/doublewiring.jpg

 

the only real diff in mine is that i wired the volume pots to be independant, by putting the "hot" from the pickups to the wiper of the associated pot rather than using the wiper as output from the pots, as i understand that was the traditional gibson style of wiring them for pickup & associated electronics independence.

 

also added a small treble bleed to the pots, 100k/47pf like i usually do...

 

i don't remember the gibson having this issue, perhaps because it had a master volume tone for each pickup position (ie: both neck pickups/both "both"/both bridge pups) rather than each neck.

 

if i DO try the series wiring, all i need to do is make sure that the output of one neck feeds the input of the next, right?

would i need to add another switch to the guitar to pull that off?

 

sorry for all the questions!! i appreciate your time bro, thanks!!

[myles_rose]

It seems contraindicated but in some circuits when there is less resistance there is less gain or output. Parallel drops the resistance.

 

I would find a print of a setup that you liked and duplicate that setup right down to the values of the tone and volume pots.

 

Don't add resistors into the circuit just to raise the resistance, it will change the tone and pickup response. The pickup has it's own resistive aspects and we do not want to add anything external.