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Topics - nosaj

Amplifier Discussion / Lab5 Compressor not engaging
August 14, 2023, 06:06:28 PM
i have a Lab5 that seems to be having a issue with the compressor not engaging. The way I understand it compressor rolled all the way to the left at -18 should be the most sensitive but it doesn't seem to matter any position of the compressor knob. it just doesn't work. Any help I can get would be greatly appreciated.
When powering on sometimes it will light for a sec then go off so the LED is good.
Schematics and Layouts / ibanez tbx15r schematic
June 08, 2020, 08:39:25 PM
Looking for a ibanez tbx15r schematic. I have one that is low vol. Inputting sine at vol or gain pot it is still low. Using the cd input the power amp is working properly.
So if anyone has one that would be great.

Amplifier Discussion / ST4151V power amp chip
December 11, 2016, 03:05:12 PM
I have a ST4151V  chip  I'd like to know how to go about testing it for shorted outputs.

I have the datasheet but not sure I quite get it.

Thanks, nosaj
I've got a Peavey xr600b   that had a shorted output transistor on it.

I replaced all 8 TO3's and the 4700/63v and the 1000/35v caps.
The + - 52 rails are good and the -+15rails are good.

Running some music in the AUX and Monitor inputs or any of the 6 channels
The volume is real low.  But if I lineout the amp to another amp it's decent sounding with  a little hiss when cranked up  ...  I diid look over the solder joints  nice and silvery.

The sand resistors tested ok on the board.  Any suggestions on how to proceed?

Wharfdale PM700 SMPS intermittant turn on
I've picked up the wharfdale PM700 PA again in hopes of making it stable. Sometimes it will turn on and just play fine other times you have to pop the on/off switch several times to get it running.

Monitoring the -+ 63 v rails and the 15v rails when it doesn't come on they produce on a few volts. The largest caps have been replaced. The little fan always comes on. I have this power supply schematic that utilizes the same smps controller chip and a lot of it looks very similiar to what I have.
From what little my brain has gathered SMPS supplies need a kick start to get them oscillating to produce the voltage kinda of like a startrun capacitor on a AC motor. But not sure where I should be checking.
Any helps would be greatly appreciated.

If the voltage regulators are iffy not putting out a clean 15v would that cause the SMPS to be intermittant?

I've got and SD-2 the effect won't turn off.  Effect works as well as all the dials and crunch lead selector just won't turn off when you hit footswitch.  I hooked my meter up to the leads on the circuitboard push button meter moves to right let go goes back left so the switch is good.  Not sure where to go from here.

Amplifier Discussion / General amp health checks
May 21, 2015, 09:13:26 PM
Does anyone have a generic checklist they do when checking the health of a solid state or a tube amp?

I just picked up a randall RG 235 DS head and 2 stereo spks for $60 output seem audibly low.  Does anyone have a schematic for it?

Caps are first thing to be replaced but just wanted to check values as I see some mods in there.

Amplifier Discussion / Wharfdale pm700 pa schematic?
September 08, 2014, 07:21:41 PM
I have a Wharfdale PM700 pa that has no output through the preamp section. Output works fine. Any chance anyone has a schematic buried somewhere as Wharfdale is unresponsive.