Pintek PS-1005

[mat]

Would this scope be suitable for tube amp testing ?

http://www.testmart.com/sp.cfm/ANAOSC/P ... 005/1.html

[Johnhenry]

Mat, Everybody has thier own opinion about Scope's, I got by for about 25 year's useing 2 old Tektronix 454 scope's, they were Cheap, Reliable and easy to use.
100 MH is more than you'll ever need for tube work, but if you repair hi-end audio equipment like keyboards or synth's, you would need plenty of scope like the one your looking at,
there are a few basic's about scope's that need to be looked at when purchasing one,
it need's a probe that can handle being stuck into high voltage, like a 10x probe,
it needs to be recently calabrated for accuracy,
and make sure all function's work.
i'm sure other's will have more input for you but hope i helped you in some way.
Johnhenry

[mat]

Thanks Johnhenry for the answer.

The thing is I could loan one (PS-1005) from my workplace. I was wondering about the 400V max input voltage. My D-clone has 485V on the EL34's.

Sorry but what does 10x probe mean

Btw. I just printed few scope instructions, have to go trough them..

[billv]

10x drops the voltage at the scope input by a factor of 10. With that in place, your amp's 485vdc becomes 48.5vdc as measured by the scope.

http://en.wikipedia.org/wiki/Test_probe

Gotta love wikipedia

[benjoi]

10x drops the voltage at the scope input by a factor of 10. With that in place, your amp's 485vdc becomes 48.5vdc as measured by the scope.

http://en.wikipedia.org/wiki/Test_probe

Gotta love wikipedia

Hurray for "The W"! (A nickname David Crowder gave Wikipedia in his book "Everybody Wants To Go To Heaven But Nobody Wants To Die or The Eschatology of Bluegrass" good read if you want to know more about death, the soul, or the history of bluegrass )
I love Wikipedia.
Sorry I'm so off topic
I wish I new how to use a scope or had access to one. (there back on topic, kindof )

[mat]

10x drops the voltage at the scope input by a factor of 10. With that in place, your amp's 485vdc becomes 48.5vdc as measured by the scope.

http://en.wikipedia.org/wiki/Test_probe

Gotta love wikipedia

Billv,

Ok the 10xprobe has 1M + 9M resistors on it + caps accross the R's. It drops the voltage ten times. Thanks for the link !

Someone already here wrote to put up an instruction how to use the scope with amps. That kind of info (for beginners) would be very cool. To know what are the most important settings to choose on the scope and how to nail say the spot of the oscillation on the amp etc.

Btw. would it be ok to feed the amp with mp3 player that has sinewave recorded into it when using the scope ?

[Johnhenry]

Mat, your MP3 would work, you need to inject about a 600, 800, and a 1 k signal through the input, it really helps if you could pick up an older signal generator off the net, and a Dummy load for what ever amperage
rating your amp need's on the speaker load, you don't want to listen to the high pitched sqeal's your amp would make if still hooked to a speaker and hit with a sig. gen. !
i'm gonna set my work bench up in a few day's, if you'd like some picture's of all my old analog test equipment, i would be more than glad to show you pic's as i set up to build me an amp, which i have never got to do in 25 yr's of amp repairing, mind you, this old junk is as old as me, and i'm retired, so that give's you a clue !, my test equipment is still the real deal if your gonna work on tube's, mostly because i can calibrate this stuff and repair it when neccesary, I know they make newer and neater stuff, but for the most all the new junk is throwaway,
Johnhenry

[mat]

Mat, your MP3 would work, you need to inject about a 600, 800, and a 1 k signal through the input

,

Sorry about the stupid question but should I combine and record all the 600,800 and 1k sine waves to the one mp3 file that I run into the amp?.....

it really helps if you could pick up an older signal generator off the net, and a Dummy load for what ever amperage
rating your amp need's on the speaker load, you don't want to listen to the high pitched sqeal's your amp would make if still hooked to a speaker and hit with a sig. gen. !

I'm trying to troubleshoot a Dumble style HRM with couple of EL34's in it. I think it is about 50w. I'm searching for a proper powerresistor for the dummy load.

i'm gonna set my work bench up in a few day's, if you'd like some picture's of all my old analog test equipment, i would be more than glad to show you pic's as i set up to build me an amp, which i have never got to do in 25 yr's of amp repairing, mind you, this old junk is as old as me, and i'm retired, so that give's you a clue !, my test equipment is still the real deal if your gonna work on tube's, mostly because i can calibrate this stuff and repair it when neccesary, I know they make newer and neater stuff, but for the most all the new junk is throwaway

,

I would really like to see pictures I read from tonelizards site that beginners (like I am) maybe shouldnt try to restore old tube based scopes, but old gurus (like You) that know how to adjust and repair those things can use them all right.

I'm going to try the mp3 - PS-1005 combination and see what I can get to the scopes screen. If there is unwanted oscillation anywhere, how does that show on the scope ? Unclean looking sine wave ? Sorry I'm such a noob

[Johnhenry]

Mat, First off, There's no such thing as a Dumb or Stupud Question,
record them, it should work, i've never tried it that way, but it should work.
I drove my Dad crazy askin question's about his repair bench when i was a kid,
and i'm still learning somethin new about every day, i luv reading the post's here and other place's for more info. i never get tired of learning about tube amp's and there's new idea's poppin up all the time.
my dad helped me build my first Heathkit Scope from a kit when i was 12, and i'm not gonna tell ya how many thing's i smoked learnin how and why to use it !
a scope can help you find a lot of problem's very quickly, and then there are other problem's that will help you develope your other abilty's, Nose, Eye's, and ear's.
when you get your Dummy load built for the wattage & ohmage you need, then you can start off by learning where you want to hook your probe to get a reading from the amp, i started out by hooking up at the speaker output jack and looking at the waveform i was getting there, then as i would crank the volume up i would start to see some spike's appear, it's called the crossover notch where the amp starts to get dirty, as you read more about this you'll find that bais will change this notch, the dirtier the amp is baised the sooner these notch'es appear, the cleaner the bais the later they appear as the volume is turned up, you can bais with the scope but i think that there are better way's to bais an amp, if it's one your use to working on, the ear's can tell you more about what volume level you want your amp to break up at ! when i do it with my ears i still check with my meter to make sure i'm not over or under baised,
You can also start out testing for waveform's on the downstream side of your coupling cap's that are in your preamp, there should be no D.C. on this side of the cap so you should be looking at just the waveform of the signal passing through the coupling cap.
If you probe on the voltage side make sure you are useing the high voltage probe, !
when you probe and move the wire's around you can watch the scope for lead dress problem's.
i alway's use an old wore out drumstick to probe with, they're normally free !
here's some of my old Equipment, an Eico mod 147 signal tracer, also work's great for pedal builder's to trouble shoot thier build's,
an Eico mod 377 Sig. Gen.
A Heathkit mod IT 28 cap tester, the best of it's kind, you can bake cap's in with it, test for leakage, shorts, and capacitance.
various decade box'es, analog meter's, varible power supply's, and my Variac.
I use a Fluke DVM most of the time !
i'll post some pic's as i get my bench back together.
i'm also sure there will be other's here that will show some of thier bench's and test equipment.
Johnhenry

[mat]

Thanks Johnhenry for a very informative post !

[Tubetwang]

Great post Jonhhenry!

Thanks!!

[Johnhenry]

I thought you might like to see my Dummy load ! i set my fluke next to the resistor's so you could get an idea of the size of these babe's, they are 20 ohm, 75 watt Dale precision resistor's, i've got them wired for 2 ohm's and 4 ohm's,
[IMG768]http://i199.photobucket.com/albums/aa33 ... ure076.jpg[/img]

[IMG768]http://i199.photobucket.com/albums/aa33 ... ure075.jpg[/img]
Johnhenry

[Tubetwang]

i have these... http://www.partsexpress.com/webpage.cfm ... oup_ID=340

[jjman]

i have these... http://www.partsexpress.com/webpage.cfm ... oup_ID=340

I ordered a bunch of stuff from them last night. Only thing not in stock was the 8ohm 100watt dummy load.