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Messages - ilyaa

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1
Tubes and Hybrids / Re: Mesa Triple Rec Woes
« on: March 24, 2020, 04:23:45 PM »
kay so V2:

if i ground pin 7, hum dies

if i short pin 7 to pin 8, hum dies

if i ground pin 2, hum gets quieter but doesnt die

if i short pin 2 to pin 3, hum dies

if i open the 475k going to pin 2, no noticeable change

if i open the 475k or the .02 uF going to pin 7, hum dies

so sounds like problem is in V2, but where???

ive tried opening all of the components to no avail.....wudya guys think?

2
Tubes and Hybrids / Re: Mesa Triple Rec Woes
« on: March 18, 2020, 01:49:56 PM »
thats the one ive been using...

whats mystifying me is that the circuit around V2a is just not matching up between schematic and amp

on the schematic there is a jfet there across that 475k going to the grid - on this amp, a relay goes across that resistor, and with the amp off that resistor measures short across...

that 15 uf from the cathode is also going to a jfet, not a relay....

in other words, that part of the schematic does not match up, and it seems to be where the problem is coming from but im sort of reaching in the dark here....

any thoughts??

3
Tubes and Hybrids / Mesa Triple Rec Woes
« on: March 16, 2020, 07:13:54 PM »
hey team!

trying to stay busy and keep working as the world burns....

and this stupid mesa triple rectifier is not helping my mood!

it has a weird hum (ground-esque) -

mostly on channels 2 and 3 but sliiight hum on channel 1, as well.

it stays, but quiet, if i pull V1 and goes away completely if i pull V2 -

its def in the preamp (half-split the amp, etc.) -

if i scope i see weird noise on pins 1, 7, 8, 6 of V3 that is totally not knob dependent - still there with knobs all the way down, and only the gain knob affects it. but if i cut out the previous part of the circuit, around V2, it goes away.

SO its clearly something around V2. i suspect some of the jfet/darlington muting stuff, but its gotten kind of hard to troubleshoot because i only have a dual rec schematic and it doesnt seem to match 100%.....

does anyone have a good triple rec schematic?

PS its not the preamp tubes i swapped em all and ive already replaced most of the Jfets and Darlingtons and smaller filter supply caps.....no change!



6
Tubes and Hybrids / Laney VC30 Output Transformer
« on: December 12, 2019, 01:06:25 AM »
if you were replacing a blown OT in this 30 Watt, 4xEl84 amp, which one would you get?

https://www.mojotone.com/amp-parts/Output-Transformers/Black-Brown-Vibrolux-Tremolux-Output-Transformer-4-8-OHM

or

http://www.triodeelectronics.com/22bastou.html

(not sure if they have that one - i e-mailed em)

or

https://www.mojotone.com/amp-parts/Output-Transformers/GA30RV-RVH-Output-Transformer

or

any other suggestions?

part of my issue is the stock transformer thats in the amp is very small - its snuggled between the second preamp 12ax7 and the PI - would like to find something small so i dont have to destroy the chassis putting the new one in.....

thank you!

7
Amplifier Discussion / Re: Gallien Krueger 800RB
« on: August 19, 2019, 03:42:15 PM »
Finally got my hands on the speaker -

Autopsy results point to DC condition -

https://ibb.co/VjKdSzD
https://ibb.co/9WjmPJ5
https://ibb.co/TR55dgC

Agreed?

If the Amp is testing fine on the bench - any thoughts as to how I’d go about tracking this DC failure down??

8
Amplifier Discussion / Re: Gallien Krueger 800RB
« on: July 23, 2019, 01:58:45 PM »
let me see if i can get my hands on the blown speaks -

how would overpowering vs. a DC fault look differently on a blown voice coil?

9
Amplifier Discussion / Re: Gallien Krueger 800RB
« on: July 23, 2019, 03:03:24 AM »
i am - thats how ive been testing it -


10
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....

11
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

12
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....

13
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!

14
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?


15
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!

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