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Messages - ilyaa

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31
Amplifier Discussion / Re: Gallien Krueger 800RB
« on: July 23, 2019, 03:03:24 AM »
i am - thats how ive been testing it -


32
Amplifier Discussion / Gallien Krueger 800RB
« on: July 22, 2019, 03:22:39 PM »
frustrating issues -

this amp has blown a few woofers - a pair of 10s in a 4x10 and a beefy EV 15 - it blew the 10s after about an hour and a half or so and blew the 15 in under a minute -

problem is, on the bench, it has no measurable issues. no DC on the output - shows me a perfect sine wave at full power on the scope - runs for as long as youd like with no visible problems.

im hesitant to plug it into an actual speaker because i dont wanna blow anything - any ideas what could be happening?

i asked the client about cabs and speaker wiring - the cabs and speaker cables were being used with other amps with no problems.

hmmmm....

33
Amplifier Discussion / Acoustic B-2 collaboration series schematic
« on: July 05, 2019, 09:05:04 PM »
Hey

Looking for a schematic for this amp

Particularly interested in the power amp - Zobel resistor blown, no way to tell what it was.

Thanks guys

34
Amplifier Discussion / Stramp hybrid schematics anyone?
« on: April 02, 2019, 01:01:40 PM »
hey!

recently came across a crazy old gem -

a Gun (United Sound Company) Lead 200

it looks just like this: http://www.vintagemusicshop.sk/?p=67295

with some researched i figured out its a later model Stramp - apparently, after he sold Stramp to Dynacord - because mine is a solid state preamp and tube power amp (with a tube PI). 100W 4xEl34 power section

has anyone ever seen a schematic for this hybrid?? its in rough shape and id love to get it going....

35
Amplifier Discussion / Re: Polytone 102 Tremolo
« on: February 01, 2019, 01:29:09 PM »
thanks, guys!

lamp was on, but no oscillation -

replaced C45 and C46 - the phase shifting caps - and were back in business!

those were weird old black boxy caps - prob dried out just enough to not do their job in this application -

vibrato sounding great!

had to reduce the gain on the reverb a bit - it was feeding back - but amps put together and back in action!

thanks again!

36
Amplifier Discussion / Polytone 102 Tremolo
« on: January 24, 2019, 02:02:30 PM »
finally got this amp almost back to life -

the power amp was busted and, because i could not find a schematic that seemed to match the amp i was looking at, i figured id just replace it with a simple class D thing. got a kit online and wired it up - it even fit the heatsink with no modifications necessary! - and the amp is working fine.

last step: the effects. the reverb is a bit weak (i think i can handle that), but the tremolo is not working at all. the good news is i found the right schematic! the bad news is, i really cant understand how the tremolo circuit is supposed to work - which obviously makes it hard to troubleshoot.

the right schematic is attached - can anyone with a bigger brain than mine explain how this tremolo is supposed to work? and whats that symbol by the LDR?


37
Amplifier Discussion / Simple SS Power Amp Build - +/- 40V Push/Pull
« on: December 04, 2018, 03:25:24 PM »
hey guys!

been a minute -

trying to clean out the crap pile while things are a bit slow at work -

i have this Polytone amp thats been taken apart for quite a bit now - the preamp is perfectly fine but somebody tried to "repair" the power amp and its just a total disaster.

the PT is fine and I decided I am just going to gut it and build a simple power amp from scratch so I can get this thing back to life -

I've got +/- 40V and heatsinks for two output transistors -

Also have a second, lower voltage tap (about +/- 20V) -

can you guys recommend a simple power amp build I can retrofit to this thing? its got a nice cab and a nice preamp with reverb and tremolo and everything - shame for it to die on this bench!

38
Amplifier Discussion / Re: polytone 102 schematic
« on: March 08, 2018, 01:04:31 PM »
gotta be honest - i think id be better off just rebuilding the power amp for this thing - the can does not seem to be matching up with any of the schematics - and even if it did who knows if that can is still good...

any recommendations for a simple single PNP/NPN pair output design? would rather make something that doesnt involve a dual can! +/- 30V rails...right now i have an MJ15023/2N3055 situation (what i had laying around) but id be willing to work with whatever - would like to get this thing working!

39
Amplifier Discussion / Re: polytone 102 schematic
« on: March 07, 2018, 02:33:59 PM »
anyone have any thoughts on this?

here's the thread from ampage - got into it a bit deeper but still no dice...

http://music-electronics-forum.com/t45698/

40
Amplifier Discussion / Re: Peavey Musician Series-400
« on: March 07, 2018, 02:32:10 PM »
good call -

replaced drivers and pre-drivers and we are all good!

thanks, Enzo!

41
Amplifier Discussion / Peavey Musician Series-400
« on: March 02, 2018, 02:14:13 PM »
scratching my head a bit with this one -

got it in the shop with a transistor missing from the back (TO-3 sized hole on the chassis...) -

replaced that and replaced one shorted power transistor in the power amp -

with no load plugged in i get a good looking waveform on the output but once i plug in a load not so good - flattened out and clearly there's a problem -

some voltages are not quite as they should be - none of the transistors (power or driver or otherwise) in the power amp seem to be forward biased - even though they are all measuring fine diode-test wise - in and out of circuit -

the +/- rails are good, but the bases and emitters are all stuck at 0V or thereabouts - the symmetry of this amp is confusing me so i am having a hard time trying to isolate the problem without just shotgunning the whole thing -

any suggestions?

42
Amplifier Discussion / polytone 102 schematic
« on: December 26, 2017, 11:58:51 PM »
the amp I have does not jive with any of the schematics ive found online.

(http://el34world.com/charts/Schematics/files/polytone/Polytone_Schematics.htm)

someone has definitely dug around in here before. first warning sign was that both output transistors had been replaced with 2n3055. I know occasionally youll run across a power amp that uses two NPNs but this amp has +30 and -30 rails and none of the polytone designs I've seen resemble a dual NPN thing. there was also a shorted driver. but before I dig too deep id love to see a schematic...

this amp has the proper To-3 heatsinks for the power amp. it says Polytone 102 70W on the back. its a 1x12 combo. the power amp pcb has a pair of NPN/PNP drivers for each output. currently they are 2n3053 and 2n4037s. other differences from existing schematics:uurather than being .15 ohms, the resistors on the output are 15 ohms. and rather than being 100 ohms,uthe resistors on the bases of the output transistors are 2.2K

oh yeah and important detail: there is an 8 pin TO-5 old-style IC at the input of the power amp. unfortunately all the text has rubbed off of it....

I can post a pic soon - any thoughts in the meantimeu

43
Amplifier Discussion / ampeg ss140c heat sink
« on: November 26, 2017, 02:29:02 AM »
hey!

any thoughts for a suitable replacement heat sink for an ampeg ss140c?

got a salvage amp here and the heat sink is just *gone!*

someone must have removed it used it for.....something???

like the one in this pic: https://gbmedia.azureedge.net/usercontent/gear/3421921/p2_uhxjnxoft_ss.jpg?maxwidth=500

i doubt ill find that part - so im thinking maybe some of you guys have thoughts on what a good material would be to use/where to get something easy to fasten on there??



44
Tubes and Hybrids / Re: fender bassbreaker 45
« on: September 14, 2017, 02:08:40 PM »
yeah - called em. no dice. amp is still under warranty.

he can send it back but i think he's a little hesitant to do so seeing as he has already - doesn't feel like going through the headache again and would rather have an amp that doesn't need to be mailed back to fender every few months!

i wonder: with the variable voltage thing going on in here - would it be possible to bypass the fancy  fet-controlled variable voltage stuff and just rewire this amp like a good old-fashioned normal tube amp? i think the variable voltage is just controlling the screen voltage and the bias (bias tracking or whatever its called) - anyone have any experience doing something like that?

45
Tubes and Hybrids / Re: fender bassbreaker 45
« on: September 14, 2017, 12:12:30 PM »
its gone back for a warranty repair already -

the owner wants to make sure whatever happens doesn't keep happening!

fender is probably gonna give me the 'you're not an authorized service center' spiel and the cold shoulder

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