General Forum

Re: Beomaster 5500 restoration project

tournedos — Tue, 12 Oct 2010 09:31:59 GMT

@MartinM, there are actually few caps on the tuner board that have any effect on the audio (maybe half a dozen), so that is a quick job!

Regarding static electricity or ESD, the most sensitive devices are digital ICs and MOSFET transistors. Early MOS technology ICs (from the 70s onward) didn't have very elaborate internal protection, and some of them will be destroyed if you give them a bad look! A BM3000 has none of these (perhaps leave the tuner front end box alone, as there's nothing worth recapping in there anyway as long as it works) so it is a pretty safe subject for learning.

That doesn't mean you should be careless though - in addition to what's already being said, keep the cats away, and perhaps avoid the work during the coldest days in central heating season when the air is very dry (for our UK readers: central heating is a system that keeps your house warm and dry )

This BM5500 (and the rest of the series) CPU module on the other hand belongs to the things where you have to be very careful. On the 5000 for example, both the CPU and the I/O expander chip contain mask programmed ROM, and you can't get spares anywhere except from another 5000!

Re: Beomaster 5500 restoration project

Step1 — Tue, 12 Oct 2010 07:15:29 GMT

Ideally you need an anti-static workmat. Not cheap but worth the investment. Found at any decent electronics store RS Farnel ebay?? etc.. At the very least, make sure are not wearing synthetic clothes and same with the carpet, and use an antistatic wrist strap which are cheap enough and a good earth point like socket / radiator etc...

edit to add there will I am sure be excellent walkthroughs / tutorials on the net as static is a big subject in electronics!

Re: Beomaster 5500 restoration project

davefarr — Tue, 12 Oct 2010 06:42:21 GMT

Hi Steve,

thanks for that. I just had a look at that video tutorial and also searched for capacitor replacement and found a really good video which helped a lot. I've read some of Martins replies and he says it is important to earth some components so you don't fry the PCB but I'm not sure how to go about that either.

I have a Beomaster 3000 that is starting to hum and become unreliable so maybe I could have a go at that.

Give me a living body and I can make it work, electronics is a dark art to me!.

Dave.

Re: Beomaster 5500 restoration project

Stonk — Tue, 12 Oct 2010 03:47:20 GMT

davefarr:
I'd love to be able to do some basic electronic work on some of my speakers etc - cap replacements for example but again, wouldn't know even the basics of soldering correctly.

With your interest in the older gear it probably would be worth looking HERE for inspiration.

I ordered a cap kit for a BM3000-2 from Martin a few years back and he supplied photographic instructions that were wonderful - I had never tried component swapping before. In fact a BM 3000 is probably a good unit to start on as the caps are all quite easily accessable.

Steve

Re: Beomaster 5500 restoration project

davefarr — Tue, 12 Oct 2010 02:32:22 GMT

I'm no techie but that looks mighty impressive to me. I wouldn't know where to start and would probably fry all of the PCB's as soon as I took the cover off. I've just taken the amps off a pair of Beolab Pentas to send to Martin for servicing and I was sweating!.

I'd love to be able to do some basic electronic work on some of my speakers etc - cap replacements for example but again, wouldn't know even the basics of soldering correctly.

A nice thread introducing this would be ideal for several of us if anyone would like to do one.

Dave.

Re: Beomaster 5500 restoration project

elephant — Mon, 11 Oct 2010 14:51:16 GMT

You are very talented

and very brave !

congratulations on the journey so far

Re: Beomaster 5500 restoration project

MartinM — Mon, 11 Oct 2010 02:44:08 GMT

Time to sit back and enjoy.

Next on the to-do list is modifying the pre amp out to be a true pre amp out, not just driven off the speaker output.

May also recap the tuner board and replace the muting relay.

Re: Beomaster 5500 restoration project

MartinM — Mon, 11 Oct 2010 02:37:42 GMT

Next is the pre amp board. Almost all caps here replaced with WIMA. I replaced the OPAmps with OPA2134 units. Decided to use sockets here so that I could experiment with different types of OPAmps later on.

CPU Module next. This was quite tricky to get into as the top cover had been soldered in part to the metal frame and proved to be a great heat sink, stopping the solder from melting. Two caps to replace here.

Preamp board and CPU module back in place. I also replaced the axial caps on the front display board and adjusted the display brightness as per service manual. The two large filter capacitors have been replaced with Cornell Dubilier caps. The originals are 35mm * 50mm. The replacements are slightly shorter at35mm*40mm. However, the clips still hold then firmly in place.

Having adjusted the no-load current as per SM, the air flow guide is now back in place and Filter caps mounted.

Beomaster 5500 restoration project

MartinM — Mon, 11 Oct 2010 02:29:02 GMT

A while ago I replaced the Caps and opamps in my Beomaster 7000 using, in part, the excellent article found on this site written by Die_Bogener. That upgrade made a significant improvement to the sound quality! This inspired me to upgrade my BM5500 as well which was in sore need of some attention. So here is a quick guide to what I’ve done to date:

BeoMaster 5500 in its original state. The rear heatsink on this particular one would get quite hot, even at low volume in a short space of time.

The BM completely stripped. I could then give the chassis a thorough clean.

Transformer, fan control board, wiring loom and Power/Amp board installed. Caps in the Audio path have been replaced with WIMA (Red caps)units and all other electrolytics with Nichicon 105 degree low ESR (Type PW and HE)units. I also replaced the two no-load current trimmer resistors with Bourns Cermet trimmers (Blue units top center close to heat sink).