Hi,
I need some advice on this amp. All the filter capacitors on this amp have gone dead. There are two 1250uf, two 2000uf and three 500uf caps. This caps are no more available. There are either higher or lower capacitance on the market. Which should I replace with. The ones with higher capacitance or lower capacitance. Please advice.
Thanks
Carlos
I need some advice on this amp. All the filter capacitors on this amp have gone dead. There are two 1250uf, two 2000uf and three 500uf caps. This caps are no more available. There are either higher or lower capacitance on the market. Which should I replace with. The ones with higher capacitance or lower capacitance. Please advice.
Thanks
Carlos
Use the nearest preferred value. 1250u would be 2200u and 1000u in parallel. Aluminium Capacitors | RS Components
2000u would be 2200u, 500u would be 470u etc
Ensure the voltage is equal to or exceeding the original.
Hope that helps.
2000u would be 2200u, 500u would be 470u etc
Ensure the voltage is equal to or exceeding the original.
Hope that helps.
Hi JonSnell, there is a slight typo here... it should be 220u + 1000u
Also, 1500u is the nearest standard value - will be fine.
Cheers,
Valery
You could make a nice gift to your Stereo70 mounting a pair of 2200uF capacitors in place of the couple of 1250 ones.
It's a sane rule of design in a single voltage source amp, keeping capacity of main capacitor double of that one used as output capacity, that here is 2000 each channel.
The diode bridge fitted on Stereo70 can carry the increase of capacity, so no worry for "fried" diodes.
The result will be a more rugged output especially at lower frequencies and high level of emission.
It's a sane rule of design in a single voltage source amp, keeping capacity of main capacitor double of that one used as output capacity, that here is 2000 each channel.
The diode bridge fitted on Stereo70 can carry the increase of capacity, so no worry for "fried" diodes.
The result will be a more rugged output especially at lower frequencies and high level of emission.
Hi Carlos,
I have a Stereo 70 which I completely restored a couple of years ago so I think I may be of some help here.
For the two largest big filter caps I used Panasonic 2200uF 200v TS-ED series and for the three smaller ones I used Panasonic 560uF 200v TS-ED series.
It's also very much worthwhile rebuilding the four PCB cards with new electrolytics while you're at it (hint radial caps with the legs slightly spread will fit). Just select good quality caps of nearest or next highest standard value e.g. 16uF becomes 18uF etc.
I also recommend checking and adjusting the quiescent current on each channel and my top tip here is that replacing aged potentiometers with some nice new sealed multi-turn ones will make this much easier.
My Stereo 70 sounded MUCH better after the rebuild and is really quite a nice little amp.
Another tip is to use the DIN type tape-in socket on the front fascia with the tape monitor button selected. This bypasses the pre-amp cards and you'll get a slightly crisper sound.
I have a Stereo 70 which I completely restored a couple of years ago so I think I may be of some help here.
For the two largest big filter caps I used Panasonic 2200uF 200v TS-ED series and for the three smaller ones I used Panasonic 560uF 200v TS-ED series.
It's also very much worthwhile rebuilding the four PCB cards with new electrolytics while you're at it (hint radial caps with the legs slightly spread will fit). Just select good quality caps of nearest or next highest standard value e.g. 16uF becomes 18uF etc.
I also recommend checking and adjusting the quiescent current on each channel and my top tip here is that replacing aged potentiometers with some nice new sealed multi-turn ones will make this much easier.
My Stereo 70 sounded MUCH better after the rebuild and is really quite a nice little amp.
Another tip is to use the DIN type tape-in socket on the front fascia with the tape monitor button selected. This bypasses the pre-amp cards and you'll get a slightly crisper sound.
Why would you use 200V capacitors?.
Is that a typo?, where would you get 18uF capacitors, it's not a standard value - next would be 22uF.
I was always VERY happy with the sound of my Stereo 70, I only changed it because it wouldn't 'play nicely' with the Trio/Kenwood three head cassette deck I bought - the 70's a nice amp, but the tape socket is wired a bit strangely.
No you don't need such high voltage ratings but they aren't going to do any harm and will help with longevity. I was simply trying to be helpful by giving Carlos a specific example of a capacitor which he can easily order, is good value for money and sounds decent.
The Farnell part number for the 560uF caps I used is 119618. An advantage of these is that they're the same diameter as the originals so will fit into the original clamps without any modifications.
The Farnell part number for the two big 2200uF caps is 1198616. These are smaller diameter (35mm) so you'll need to fit some new clamps if you use these.
On the power amp cards C30 is 16uF which is an unusual value. 18uF might not be a 'standard' value as such but you can get 18uF in many widely available commercial capacitor ranges from Panasonic, Rubycon etc. I used Panasonic FC in mine.
The Farnell part number for the 560uF caps I used is 119618. An advantage of these is that they're the same diameter as the originals so will fit into the original clamps without any modifications.
The Farnell part number for the two big 2200uF caps is 1198616. These are smaller diameter (35mm) so you'll need to fit some new clamps if you use these.
On the power amp cards C30 is 16uF which is an unusual value. 18uF might not be a 'standard' value as such but you can get 18uF in many widely available commercial capacitor ranges from Panasonic, Rubycon etc. I used Panasonic FC in mine.
I ditched the clamps and glued the new smaller capacitors in my ST120 with rubber cement. One can use 3M weatherstrip adhesive from the auto supply. A good rubber adhesive comes in dispenser tubes from the home store as wallboard adnesive, but usually you only use a tube once then it dries up. This mount allowed me to use >3000 hour service life radial lead caps from CDE, United Chemicon, Panasonic or Nichicon.
Strain relieve the connecting wires to snap in caps lead by drilliing 4 holes in an insulator board and looping the connection wires through that before connecting to the can tabs. The can tabs poke up through two holes in the board. I had my amp heat up enough durring a 4 hour choir rehearsal to melt the solder, then the solid core wire jumped up off the output capacitor, touched the top, and blow the output transistors in a big ball of fire. THe looped wires would be better contolled if the amp got that hot.
Strain relieve the connecting wires to snap in caps lead by drilliing 4 holes in an insulator board and looping the connection wires through that before connecting to the can tabs. The can tabs poke up through two holes in the board. I had my amp heat up enough durring a 4 hour choir rehearsal to melt the solder, then the solid core wire jumped up off the output capacitor, touched the top, and blow the output transistors in a big ball of fire. THe looped wires would be better contolled if the amp got that hot.
Last edited:
16uF certainly WAS a very common value
I've never even seen an 18uF?.
The wide tolerance on electrolytics means it makes very little difference of course.
Priceless! Anyone rebuilding the preamp and power boards on these - make sure you use a low wattage soldering iron as the tracks seem to be glued, rather than the old etching process we did in the '60s. A 15w is fine, but a 25w is too deadly on those stubborn lock-fit BC148's.
I love these amps, Ive 2 of them (you can NEVER own too many amps) having been introduced to one in a mates brothers HiFi shed in the mid-60's.
I always vowed Id get one when I could afford one- and it took about 30 years...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.