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Can anybody tell me what this is?

J

jonawald

New Member
Hi all.
I have been on a learning quest about audio and audio equipment for a few years now after having to help chose sound equipment for a small school auditorium and setting up various sound systems in classrooms. I thought I had a basic working idea what the inside of an amplifier is supposed to look like after having worked on the insides of several integrated and stand alone amps.

Last weekend, somebody gave me an amp. There were few markings on the outside, nothing to indicate where it was built or by who. So I thought I would check inside to see what I could learn. The guts, or relative lack of them really surprised me. Can anybody help me understand what's going on from the pictures?
 

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My guess would be a home built power amp. The faceplate and LEDS look like a factory made unit, insides look experimental.

Extreme caution is advised on power up.
 
IIRC ILP sold kits. That looks like one of them. The case in particular appears to be of the limited production run type. The holes for the LED display and those on the back panel indicate the same. The amplifier module saying ILP on it reinforces that thought.
 
I haven't seen one of those in (a lot of) years! When I was in high school (ca. '79) me and a couple of friends dabbled as disc jockeys for school dances, hockey parties, etc. We built one of those ILP based amps for our business. Very simple to build - five connections on each amp module, a power supply, power switch, heat sinks and a case. (If 3 17 year olds could do it without electrocuting themselves, anybody can!) There's a bit of info on the web about these. ILP is a British company that appears to still be in business.

I have no idea where the amp is now, but it served us well for a couple of years until we all moved on to the rest of our lives. I had the ILP module catalog in my boxes of reference material (or junk, as my wife called them) for the longest while, but purged them on a move several years ago.

Have you hooked it up and tried it yet?

SteveH
 
BigElCat said:
This is the first I've heard of ILP.
Click to expand...

Being a British company, they may not have made huge inroads into the U.S. We sometimes saw more of the British stuff up here in Canada. I recall that we got the modules from a pro sound shop in Kitchener, Ontario.

Around the same time, I built a 'hi-fi' amplifier kit from Sinclair Electronics (also a British company). It was called the Stereo Sixty and came with a power supply, pre-amp board and two amplifier boards. Basically you used crimp on edge connectors to interconnect the boards, built a chassis and away you went. Never did get it to work all that well and finally tossed the lot years ago.

http://www.nvg.ntnu.no/sinclair/audio/hifi.htm

SteveH
 
Hi. Thanks for all the replies. I haven't fired it up yet. haven't had a chance yet. Might go for it later today though if I get a chance. Any idea what kind of power it is able to put out? Based on the 120 above the LED meters I guessed around !00. Is that reasonable? Or is it way lower?

Jonathan
 
As confirmed by others, these are ILP power amp modules. These were popular when I was growing up (still am), I remember drooling over the power outputs of these modules when I was still only getting pocket money. I could never afford the modules, let alone the cost of the power supply that was recommended.

I would recommend tidying up the wiring a bit, it looks like one of the signal feeds runs right beside the transformer. The speaker switch doesn't look like it's that meaty either, you might want replace that. Maybe even replace those big caps with new ones, Nichicon or Panasonic 10000uF 50V caps start at just $5 from Mouser? I seem to remember some magazines back in the day testing these modules, and thought they had a really good sound. The specs seem to be as good as what you'd find in the same era.

I would be interested to see pictures of the VU meter board as well.

Lee.
 
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I will take more pictures when I get a chance. Will also look at the caps and wiring before I fire it up. Am thinking of using it to power a couple of stage monitors. Should work for that right? Not even sure what the monitors are going to be at this point yet.

Jonathan
 
Ok finally got a chance to take another look at that amp. First off when I plugged it in without speakers. I noticed that the LED indicators were wacky. Left channel was lit up to halfway even with no input and volume know at 0. There was an LED on halfway up the right channel too. I didn't know what to make of this. Was there an input that would fry my speakers as soon as I plugged it in?

After careful consideration, I decided to plug in a cheap speaker that I wouldn't loose sleep over it it blew up. One channel worked fine, the other channel managed a few weak bursts on high energy moments in the music then died completly.

I was worried about those LED indicators so I completely disconnected the audio input side. Turns out even then, the LEDs on the Left channel stayed lit up. I concluded somebody musht have miswired something. Pictures below. Any idea how to fix this?

I decided to rewire the left amp to the right pot to see if things would change. This, I figured, would narrow it down to the amp or the pot. If it worked it would be the pot if not it would be the amp.

It didn't work.

THEN, I thought of checking the fuse on the dead channel. It was blown. The wireing at the pot of that channel was messy and could easily have been shorted out. I resoldered everything at that pot and changed to a longer coax as has been suggested here. Both channels work beautifully now.

Here are pictures of that LED setup. Again, it didn't work as expected, somebody goofed when they wired it up.
 

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Congratulations, glad that you got it working. As for the display, without a schematic of the LED display it's difficult to give advice. You can do it the hard way be tracing and diagramming all the wiring. Of course you can continue to bypass the display as it is only eye candy and has no effect on performance.
 
I'll probably take a good look at it. If I can figure out how to get it going i'll fix. I won't waste too much time with it. Other things to do.
 
These PDF files might help you figure out the VU meter circuit. It might be a good idea to just rebuild it again. The Velleman circuit is particularly good because it has a cheap op-amp in front of the more expensive bar-graph driver chip. I have two of these kits by the way.

Lee.
 

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O, great. some scems will go a long way to helping me. I was thinking of totally rebuilding it. Seems simple enough. That way I can learn a bit, and get it working as it should too.
 
Ok, I didn't find anything in the PDFs that looked quite like it matched with the layout of the board for this unit. So I drew up a schematic fo what this board looks like.

First attempt ever at drawing a scematic, Hope it is readable.

Some notes.
1. There are two coils drawn in that I am not entirely sure are actually coils. They could be diods or resisters. I did my best guess based on the appearance.

2. Same with a pair of caps. I assumed those yellow cylindrical things that are connected to the "coils" are caps.

3. I find it strange that Pin 3 on the transisters goes to - in addition to the other circuit. Hopfully you will see what I mean by looking a the scematic.

Edit. I noticed I had left out one resistor from Pin 8 to - on both sides. Lots of the solder joints are poorly done.

the layout looks much like the first half of the extended range VU meter from LM3915.PDF.
 

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actually I sort of lied about that being my first ever drawing. :) that is the third edit. The first two didn't look so good. Looks way more messy with all the - wires drawn in.
 
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