Amstrad tower system TS90 - UK Vintage Radio Repair and Restoration Discussion Forum

pletevl · 26th Nov 2018, 4:20 pm

Hi all,

I'm in the process of replacing all the capacitors in my Amstrad TS90 to try and get the thing going again. Some of the capacitors are stuck down with glue. Can anyone explain why, and if I should glue the new ones down?

Thanks.

Pete.

TrevorG3VLF · 26th Nov 2018, 5:59 pm

The seas in La Manche can get very rough. Just treat the device with TLC (tender loving care).

The advice given here over and over again is to replace components only if they are faulty.

SiriusHardware · 26th Nov 2018, 6:09 pm

Larger radial capacitors are some of the top-heaviest components on a PCB but are usually only secured in place by two solder joints: Solder is a very soft metal. It was therefore not unusual for them to be glued to the PCB as well as soldered, to make sure they stayed in place during initial transit from the factory to the end user, and if the unit got moved around a lot afterwards.

If you don't plan on moving your unit or transporting it from place to place every few days, don't glue them down.

I also agree with Trevor that if you are not aware of a problem potentially being caused by bad capacitors then you should probably just leave them alone. If there is clear evidence that some capacitors have gone bad then by all means replace them.

Radio Wrangler · 26th Nov 2018, 7:01 pm

Repeated stress and flexing of a solder joint will eventually cause the solder to go crystalline (small crystals) and become what's called a 'dry joint' before it eventually fails.

So larger electrolytic capacitors were sometimes anchored with a squirt of glue, sometimes a sort of air-glue foam.

Some production processes had trouble with components floating away from the board when wave soldered, or getting shaken out in transport between the component fitting area and the wave soldering machine. These people sat components on a dot of glue to hold them just for their manufacturing process.

Some Japanese manufacturers of amateur radio equipment would flood oscillator circuit areas with a rubbery adhesive to damp microphonic pick-up of vibrations. Unfortunately, years later we discovered that their chosen adhesive corroded and destroyed the trimmer capacitors. The adhesive had to be dug out with tweezers, and the trimmer capacitors replaced. It was a tedious job.

David

crackle · 26th Nov 2018, 8:33 pm

Glueing the components in place may also have prevented them from falling out whilst handling and prior to soldering.
Mike

pletevl · 27th Nov 2018, 11:02 am

Thanks everyone for the answers.

I decided to change the caps seeing as they are all 40 years old.

The unit has a problem somewhere that is making the volts drop. It seems to have a dual power supply and one of them is low.

Richard_FM · 27th Nov 2018, 3:59 pm

Wax was another substance used to secure components, favoured by factories in Hong Kong.

Studio263 · 27th Nov 2018, 5:12 pm

Quote:

Originally Posted by pletevl

I decided to change the caps seeing as they are all 40 years old.

As is the rest of it, what's your point?

Quote:

Originally Posted by pletevl

The unit has a problem somewhere that is making the volts drop. It seems to have a dual power supply and one of them is low.

I think you may be on a fool's errand there. I'd start by looking at things like the power output IC, a far more likely cause of problems like this. Is anything getting hot? If the power supply rails are being dragged down I'd guess something must be.

If you know the supply voltage is low you must have a diagram and a meter, so use these to see if there is an excess current draw. Then find it by isolating the suspects one by one. Remember it can't be anything which is fed by a resistor of any real value, which rules out most of the capacitors you are changing...

SiriusHardware · 27th Nov 2018, 10:14 pm

Pletevl, did you get your diagram from an online source? If so, please provide a link to it and we will be able to be more helpful.

As has been observed, you do have a meter. Do you also have access to a scope?

pletevl · 28th Nov 2018, 10:19 am

Hi all, I have searched everywhere for a service manual or diagram and can't find one anywhere so I am working blind.

I do have a multimeter yes and I also have a PEAK ATLAS ESR70 capacitor tester which is showing me that some caps and leaky or open circuit, that is why I have decided to change them STUDIO263.

Pete.

26th Nov 2018, 4:20 pm	#1
pletevl Triode Join Date: Nov 2018 Location: Pont Saint Vincent, France. Posts: 37	Amstrad tower system TS90 Hi all, I'm in the process of replacing all the capacitors in my Amstrad TS90 to try and get the thing going again. Some of the capacitors are stuck down with glue. Can anyone explain why, and if I should glue the new ones down? Thanks. Pete.

26th Nov 2018, 5:59 pm	#2
TrevorG3VLF Rest in Peace Join Date: Apr 2011 Location: Matlock, Derbyshire, UK. Posts: 1,378	Re: Amstrad tower system TS90 The seas in La Manche can get very rough. Just treat the device with TLC (tender loving care). The advice given here over and over again is to replace components only if they are faulty.

26th Nov 2018, 6:09 pm	#3
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,587	Re: Amstrad tower system TS90 Larger radial capacitors are some of the top-heaviest components on a PCB but are usually only secured in place by two solder joints: Solder is a very soft metal. It was therefore not unusual for them to be glued to the PCB as well as soldered, to make sure they stayed in place during initial transit from the factory to the end user, and if the unit got moved around a lot afterwards. If you don't plan on moving your unit or transporting it from place to place every few days, don't glue them down. I also agree with Trevor that if you are not aware of a problem potentially being caused by bad capacitors then you should probably just leave them alone. If there is clear evidence that some capacitors have gone bad then by all means replace them.

26th Nov 2018, 7:01 pm	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,903	Re: Amstrad tower system TS90 Repeated stress and flexing of a solder joint will eventually cause the solder to go crystalline (small crystals) and become what's called a 'dry joint' before it eventually fails. So larger electrolytic capacitors were sometimes anchored with a squirt of glue, sometimes a sort of air-glue foam. Some production processes had trouble with components floating away from the board when wave soldered, or getting shaken out in transport between the component fitting area and the wave soldering machine. These people sat components on a dot of glue to hold them just for their manufacturing process. Some Japanese manufacturers of amateur radio equipment would flood oscillator circuit areas with a rubbery adhesive to damp microphonic pick-up of vibrations. Unfortunately, years later we discovered that their chosen adhesive corroded and destroyed the trimmer capacitors. The adhesive had to be dug out with tweezers, and the trimmer capacitors replaced. It was a tedious job. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

26th Nov 2018, 8:33 pm	#5
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Amstrad tower system TS90 Glueing the components in place may also have prevented them from falling out whilst handling and prior to soldering. Mike

27th Nov 2018, 11:02 am	#6
pletevl Triode Join Date: Nov 2018 Location: Pont Saint Vincent, France. Posts: 37	Re: Amstrad tower system TS90 Thanks everyone for the answers. I decided to change the caps seeing as they are all 40 years old. The unit has a problem somewhere that is making the volts drop. It seems to have a dual power supply and one of them is low.

27th Nov 2018, 3:59 pm	#7
Richard_FM Nonode Join Date: Sep 2017 Location: Stockport, Cheshire, UK. Posts: 2,004	Re: Amstrad tower system TS90 Wax was another substance used to secure components, favoured by factories in Hong Kong. __________________ Hello IT: Have you Tried Turning It Off & On Again?

27th Nov 2018, 10:14 pm	#9
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,587	Re: Amstrad tower system TS90 Pletevl, did you get your diagram from an online source? If so, please provide a link to it and we will be able to be more helpful. As has been observed, you do have a meter. Do you also have access to a scope?

28th Nov 2018, 10:19 am	#10
pletevl Triode Join Date: Nov 2018 Location: Pont Saint Vincent, France. Posts: 37	Re: Amstrad tower system TS90 Hi all, I have searched everywhere for a service manual or diagram and can't find one anywhere so I am working blind. I do have a multimeter yes and I also have a PEAK ATLAS ESR70 capacitor tester which is showing me that some caps and leaky or open circuit, that is why I have decided to change them STUDIO263. Pete.