Bottom line: don't expect any schematics.
Spoke to Dave Belles himself, today. He considers schematics intellectual property & won't hand out or sell them.
If you DO get one, my PP account is ready.
Yeah, "reverse engineering." Compared to a Hafler XL-280*, the Belles is VERY simple. I scheched out the PCB on 11X17 paper & drew in the components.This means "reverse engineering" in case of wanted schematic.
Sorry I don't know what this means. But for all either of us knows, Belles may have used similar if not the same topology, just newer components in your 350! Google Rod Elliot. He does that in many of his power amps designs....topology: cascoded differential amp with current mirror
Has 3 transistors (FETs?), 8099s* & 8599s*, per side before the drivers (41011 one side, the other??); all discrete components, no chips;and dual BjT "LM394" in the front end...
6 bi-polars per channel in output.audio lateral MOSFET's from Exicon in the output).
I think you guessed right. Click here for a long-winded confirmation. My Belles doesn't have a bias POT. If I can get DC offset problem licked, that should be easy. I noticed a 1 or 2 resistors w/out a "twin."But I don't know the exactly recommend value for the idle current. I guess 100-150mA/each Exicon MOSFET pair.
I'll post pics of PCB too-Popper partially disassembled to draw schematic.Can you post some pictures (outside front/Rear/top view inside) ??
Yeah you won't any info on Power Modules.com about these or any other pre early-mid 90s designs*. Several times a year you'll see any of these come up for auction on ebay-that's where I got Popper, my 2nd one.I cannot find any information about the amp model "1 Series" from Power Modules/David Belles - obviously there are only few devices produced (maybe first power amp device from David Belles).
the 41011 is screwed to a heat sink that's then screwed to the PCB. I'll have to look on the heat sink side.41011 sounds like custom made BjT's from RCA/Harris - check also the logo
8099/8599 could be that type:
working on it-tough w/9 kids! I squeeze in editing (a text file)between crisses then copy/paste to a reply window.The first steps you must perform is follow:
1) create schematic diagram
Should be easy-only 3. Then check offset again? Here's where I'm fuzzy on your advice2) replace all electrolytic caps
measure w/shorted inputs (?) If offset still bad, then start the trouble shooting?If DC offset still present,
I've heard the XL280 use this*. Except for **, I do not know what any of these other terms mean. I see VAS in many other amp threads-haven't gotten to asking what it means.idle current servo circuit
differential input amp* without current source** and current mirror...
VAS without Ube current source...bootstrap cap to the output...
BTW - the asked variable resistor (for bias resp. idle current through the last stage) is to find by picture 2 about post #12 (probably Vishay/Spectrol) und looks like this:Any potentiometers on board?
Took me 4 tries to get from the 1st, confusing, lines crossed every which way, to a simple, flow, (hopefully) easy to read for some who hasn't had the hardware in front of them.
I believe one of you gurus can come up w/THE "bias solution."
I compared it to some other schematics-2 each: Hafler & Pass. I believe this design will not allow for the typical bias pot.
In the next edition I will adjust spacing in some places, complete the parts list, & post the schematic & parts list.
Just before I went to bed (@ 5am today!) I discovered the driver transistors, when viewed from "pin side," has one corner different than the other 3. W/this in mind looking @ the other, I quickly realized the "striped" driver is really the same type... UPSIDE DOWN(!) [as the other driver (041011)]
Also, in 3 places, I see 3 paralleled components w/the #15 on them & nothing else. 1 reversed polarity from the other 2. I thought they were disc caps. DMM testing reveled fixed resistance.
Next reply: schematic & parts list