Here are the innards of a "Matrix Unit" which belongs to a 70's vinatg ESS quad speaker system. These box provides bass contour cointrol and serves as an amplifirer to a 12" bass reflex speaker. Included is a pair of 900uf 50VDC units, as pictured. Should I plan on replacing these and, if so, where to find them? Thanks
Attachments
If you do think they need replacing and you can't readily get 900uF unit you can always make up the required value by having parrallel unit that give 9oouF. (i.e. a pair of 470uf in parrallel comes close.) the voltage rating should be the same or higher. They might profit from running a small polypropolene cap across them. I'm not clear what pupose they serve. Are they part of the signal circuit? If so they may be bi-polar (or non-polarised). That needs to be checked.
Hi Yanx,
Electrolytic capacitors from the '70s will definitely need to be replaced. 15 years is considered very good going for ones of this type. Sound and reliability should improve.
It looks to me as if they are the power supply smoothing caps. If this is true and this unit is also a amplifier then it may be a good opportunity to increase the capacitance here. Capacitors are a lot smaller these days. I suspect that a modern 900uF replacement would be tiny in comparison to the original and this may also cause you some problems when mounting.
Before increasing the capacitance you should check the ratings of the rectifier diodes. Any increase in capacitance may put them under increased strain so maybe swap them for beefier types. This may be an opportunity to choose fast recovery types or whatever is the current flavour of the month.
Be aware that these caps may still have potential harmful charge stored in them so consider discharging them first! A forum search should help you there or just ask here.
Do you have a close-up photo of the cap markings? Like Johnathan said, it is important to be sure that they are not bi-polar types that must be replaced with a similar type. I'm 99% sure that they are not but it is better to be sure.
If you want to have an easy life then just get hold of some 1000uf caps with the highest voltage rating you can find so that it may be a similar size and easy to mount.
Once we are sure that they are polarised electrolytic and you provide some measurements the I'm sure that someone here would help you to find replacements.
More pictures would also be helpful if you can manage it.
Kind regards,
Martin.
Electrolytic capacitors from the '70s will definitely need to be replaced. 15 years is considered very good going for ones of this type. Sound and reliability should improve.
It looks to me as if they are the power supply smoothing caps. If this is true and this unit is also a amplifier then it may be a good opportunity to increase the capacitance here. Capacitors are a lot smaller these days. I suspect that a modern 900uF replacement would be tiny in comparison to the original and this may also cause you some problems when mounting.
Before increasing the capacitance you should check the ratings of the rectifier diodes. Any increase in capacitance may put them under increased strain so maybe swap them for beefier types. This may be an opportunity to choose fast recovery types or whatever is the current flavour of the month.
Be aware that these caps may still have potential harmful charge stored in them so consider discharging them first! A forum search should help you there or just ask here.
Do you have a close-up photo of the cap markings? Like Johnathan said, it is important to be sure that they are not bi-polar types that must be replaced with a similar type. I'm 99% sure that they are not but it is better to be sure.
If you want to have an easy life then just get hold of some 1000uf caps with the highest voltage rating you can find so that it may be a similar size and easy to mount.
Once we are sure that they are polarised electrolytic and you provide some measurements the I'm sure that someone here would help you to find replacements.
More pictures would also be helpful if you can manage it.
Kind regards,
Martin.
Thanks so much for your responses. S3, the points that you make are certainly sound and oint to the fact that this particular aspect of my project is a bit beyond my current skill/knowledge level. There is a local guy whom I trust to which I will take this - he will go through it with me and I will get things brought up to date and learn at the same time.
I've looked at the photo and these look very good quality caps.
Have a very careful look for bulges and venting of electrolyte. If there is none, they are probably fine. I'd just use it.
I've got loads of very very old transistor kit and rarely does a capacitor fail. Including a Sansui 5000x that is over 30 years old - will all original parts.
Valve/tube sets on the other hand - capacitors in those drop like flies.
Have a very careful look for bulges and venting of electrolyte. If there is none, they are probably fine. I'd just use it.
I've got loads of very very old transistor kit and rarely does a capacitor fail. Including a Sansui 5000x that is over 30 years old - will all original parts.
Valve/tube sets on the other hand - capacitors in those drop like flies.
Hi everyone,
I agree that it is possible for these caps to be functioning. I seriously doubt that they are within tolerance after 30 years. I could well be wrong. It seems likely that the amplifier function, especially when driving 12" speakers, would benefit from having the full 900uF as originally intended and could well be much improved with increased capacitance.
How many decent modern solid state amps have you seen with 900uF per rail? how may of them would be happy driving a 12" speaker?
4Yanx: Your local guy, if he knows his onions, should be able to safely increase the capacitance at least a little and I suspect the performance of the unit will be improved by this.
Some caps may last 30 years but we can't say with any certainty how many will last 31. New caps would give you some piece of mind. Nobody wants electrolyte leaking inside their gear. It's not nice.
The only possible downside that I can see is that with larger caps and more power reserves for transients (bangs, thumps, kick drums etc) you may not notice that your amp is turned louder than it was designed to be. This a minor issue but I mention it for completeness.
Other things to check while the lid is off are any potentiometers (volume, tone etc) and also renew the thermal compound on the transistors. This goes off over time and the new stuff (especially the more expensive silver stuff) will do a much better job of keeping those hot things...... um....... cool. You could get away without doing this but wouldn't it be good to know that it is running as intended or better? The thermal compound should increase the lifespan of your amp.
Any other mods would probably fall into the category of tweaking.
P.S. Just replaced some very high quality slit foil electrolytic caps in a 15 year old amp amplifier with some cheap but 20% higher capacitance ones. The results were conclusive and I'd recommend it to anyone. Caps age very slowly every day so how would you notice that the sound has changed?
Cheers,
Martin the Martian.
I agree that it is possible for these caps to be functioning. I seriously doubt that they are within tolerance after 30 years. I could well be wrong. It seems likely that the amplifier function, especially when driving 12" speakers, would benefit from having the full 900uF as originally intended and could well be much improved with increased capacitance.
How many decent modern solid state amps have you seen with 900uF per rail? how may of them would be happy driving a 12" speaker?
4Yanx: Your local guy, if he knows his onions, should be able to safely increase the capacitance at least a little and I suspect the performance of the unit will be improved by this.
Some caps may last 30 years but we can't say with any certainty how many will last 31. New caps would give you some piece of mind. Nobody wants electrolyte leaking inside their gear. It's not nice.
The only possible downside that I can see is that with larger caps and more power reserves for transients (bangs, thumps, kick drums etc) you may not notice that your amp is turned louder than it was designed to be. This a minor issue but I mention it for completeness.
Other things to check while the lid is off are any potentiometers (volume, tone etc) and also renew the thermal compound on the transistors. This goes off over time and the new stuff (especially the more expensive silver stuff) will do a much better job of keeping those hot things...... um....... cool. You could get away without doing this but wouldn't it be good to know that it is running as intended or better? The thermal compound should increase the lifespan of your amp.
Any other mods would probably fall into the category of tweaking.
P.S. Just replaced some very high quality slit foil electrolytic caps in a 15 year old amp amplifier with some cheap but 20% higher capacitance ones. The results were conclusive and I'd recommend it to anyone. Caps age very slowly every day so how would you notice that the sound has changed?
Cheers,
Martin the Martian.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.