SB-220 Capacitors ?
 

I just bought an old SB-220 amplifier and have not actually received it yet.
To those that have these, what is a decent source of electrolytics for the
power supply? I plan on swapping them before I try to power it up, since I
am sure the present ones are dry.

Doug N4IJ

Doug -

Replacement capacitors are available from Mouser Electronics.

Jeff Weinberg at Harbach Electronics also carries a number of parts for the
SB-220 as well as
electrolytic capacitors. (See CAPS and SB-220 reference on left frame)
http://www.harbachelectronics.com/

w9gb
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"DOUGLAS SNOWDEN" wrote in message
...
I just bought an old SB-220 amplifier and have not actually received it
yet.
To those that have these, what is a decent source of electrolytics for the
power supply? I plan on swapping them before I try to power it up, since
I
am sure the present ones are dry.

Doug N4IJ

Doug -

Replacement capacitors are available from Mouser Electronics.

Jeff Weinberg at Harbach Electronics also carries a number of parts for the
SB-220 as well as
electrolytic capacitors. (See CAPS and SB-220 reference on left frame)
http://www.harbachelectronics.com/

w9gb
--
DO NOT use Reply.
Only reply through ARRL forwarding service to W9GB

"DOUGLAS SNOWDEN" wrote in message
...
I just bought an old SB-220 amplifier and have not actually received it
yet.
To those that have these, what is a decent source of electrolytics for the
power supply? I plan on swapping them before I try to power it up, since
I
am sure the present ones are dry.

Doug N4IJ

I just bought an old SB-220 amplifier and have not actually received it
yet.
To those that have these, what is a decent source of electrolytics for the
power supply? I plan on swapping them before I try to power it up, since
I
am sure the present ones are dry.
=================
Suggest you try to recondition (reform) the existing electrolytic caps
before replacing them .

Remove wiring from caps and charge them individually slowly via a 1or 2 Watt
, 47 KOhms resistor to the rated working voltage .
It is possible that in the first round you won't achieve that . When voltage
across cap no longer increases ,discharge via the same resistor . Charge
again ; the end voltage will be higher. Then discharge again.
When upon charging the caps voltage no longer increases measure the voltage
across the known resistor to determine the leak current. It might be
worthwhile to repeat the charge/discharge process a few times.

In the above way I have this week reconditioned a variety of electrolytic
caps the largest being 1000 microFarad -450 V.
Although the Working Voltage for this particular cap (of which I have 8 pcs)
is 450 V ,they happily accept a charge to a voltage of 510 V with an overall
supply of 550 V , hence 40 V across the 47 kOhms series resistor ,hence the
leak current is less than 1 mA.
Some old Plessey capacitors from 1974 , 200 microFarad - 450 V have
successfully received the same treatment.
I now intend to check the effectiveness by placing the caps (1 at the time)
across the output terminals of a power supply unit made from a suitable
transformer and half wave rectifier watching the voltage output wave form on
a scope at varying load.

For lower voltage electrolytic caps smaller series resistors are required .

The caps should be slowly charged /discharged ,each operation taking about
4 - 5 minutes.


Frank GM0CSZ / KN6WH

I just bought an old SB-220 amplifier and have not actually received it
yet.
To those that have these, what is a decent source of electrolytics for the
power supply? I plan on swapping them before I try to power it up, since
I
am sure the present ones are dry.
=================
Suggest you try to recondition (reform) the existing electrolytic caps
before replacing them .

Remove wiring from caps and charge them individually slowly via a 1or 2 Watt
, 47 KOhms resistor to the rated working voltage .
It is possible that in the first round you won't achieve that . When voltage
across cap no longer increases ,discharge via the same resistor . Charge
again ; the end voltage will be higher. Then discharge again.
When upon charging the caps voltage no longer increases measure the voltage
across the known resistor to determine the leak current. It might be
worthwhile to repeat the charge/discharge process a few times.

In the above way I have this week reconditioned a variety of electrolytic
caps the largest being 1000 microFarad -450 V.
Although the Working Voltage for this particular cap (of which I have 8 pcs)
is 450 V ,they happily accept a charge to a voltage of 510 V with an overall
supply of 550 V , hence 40 V across the 47 kOhms series resistor ,hence the
leak current is less than 1 mA.
Some old Plessey capacitors from 1974 , 200 microFarad - 450 V have
successfully received the same treatment.
I now intend to check the effectiveness by placing the caps (1 at the time)
across the output terminals of a power supply unit made from a suitable
transformer and half wave rectifier watching the voltage output wave form on
a scope at varying load.

For lower voltage electrolytic caps smaller series resistors are required .

The caps should be slowly charged /discharged ,each operation taking about
4 - 5 minutes.


Frank GM0CSZ / KN6WH

Try some of the surplus houses that sell Nichicon caps, they go for about $3-4
each , not like the $25 original style. Have to improvise mounting but that
is quite easy.

Try some of the surplus houses that sell Nichicon caps, they go for about $3-4
each , not like the $25 original style. Have to improvise mounting but that
is quite easy.