i'm finally getting around to rebuilding the condenser block. I have all the caps i need exept for the 2uf caps because i was unsure of what to get.
For the 2uf capacitors would that be an electrolytic and if so what direction would the neg terminal go?
any other helpful information is appreciated. Thanks.
Most people are using film capacitors for all of them. They will work better than an electrolytic. 630 volt. I will use film caps for everything up to 10 or 12 mfd. (Unless it won't fit in the original can.)
(This post was last modified: 10-12-2020, 09:17 PM by rfeenstra.)
Hello Link,
I second that ! what rfeenstra said.
Film is the way to go and they are getting cheaper in price and larger values and they will last our life time.
I rebuilt the filter block in a model 87 with electrolytic caps which is very similar to the 96 using small value capacitors and a lot of inductance. Got the rest of the chassis sorted and enjoyed the set for abt 4 months. Till one day I was listening to it and the volume dropped to a whisper. I looked in the back to find to find the 80 tube glowing beet red. Quick turned it off.
Have seen this happen before when servicing ham gear and audio amps where the tubes are pushed to their limits voltage wise. In audio amps what happens operator tried to use it w/o the speaker connected. This causes one of both of the output tube to short. Next in line is the output transformer and then choke in the power supply. Finally the rectifier tube and power transformer are toast. From a service standpoint it's not so bad you can make a few dollars but not so great for the owner.
In the case of the 87 it wasn't as bad as it could have been if I wasn't right there to take note of what was happening. I should backup a bit. At this time we where remodeling the house (2013) so the set went off to the shed till a couple of weeks ago. Got it on the bench and apart to find that the first cap in the block was a dead short. Killed by ripple current. This is what caused the rectifier to get red and angry. I'm not sure if I hadn't caught it quickly if it would have taken the transformer. I kinda wish that the diagrams that do have the + and - notations for these later '20s set didn't have them. Caps got replaced with film jobs. It's back working but need to be aligned which requires a long thin hex driver maybe longer than Steve's tool.
Off the soap box
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 10-13-2020, 12:08 PM by Radioroslyn.)
Thanks For the Replies, much appreciated.
i read something saying caps over 1uf were likely electrolytic filter caps so i had to ask.
i have film caps to replace everything else i just have to get those 2.
i prefer this old radio to live again and not suffer an ill fated death.
i just have to check all the resistors after this is done before i worry about getting a variac and slowly turning it on.
one thing at a time.
When you start looking for a variac take a look at the Mophorn on Amazon. They have several sizes. I bought the 500 VA one last July and it has been running great.
Just so you know variacs do not provide any isolation from the ac line like a isolation transformer. Variacs are auto transformers which means that they are a transformer that only have a primary no secondary. Fine to use with sets with a power transformer but if used on a set with series strung heaters use safety precautions as you would with a standard ac/dc set.
There are sets that look like ac/dc set but aren't. Cheap tube type phonos ac/dc chassis for the amp but the motor is ac. Sets that look like an ac/dc set but uses a voltage doulber in the power supply. On the outside it will be marker as 120 volts ac so you think you're ok but maybe not.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Hi Link..I’ve been using a RCA Isotap 11 WP-27A that I bought over 40 years ago. I believe it goes by VIZ Isotap now. It is an isolation transformer with output from 25- 150 volts in 5V steps. All in one unit. Can be found on eBay or other sites!
I have a question, how many watts equal 275VA and 500? I saw a different model that is both an auto transformer and isolation transformer. The primary (auto transformer side) is rated 500VA and the secondary rated @ 275VA. Had a switch and 6 outlets on the top. Was surprised that it doesn't have a fuse.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 10-15-2020, 12:23 PM by Radioroslyn.)
i was curious about VA too and i found this formula
100 volts times 5 amps = 500 Volt-Amps, 500 VA.
which looks exactly like how you would calculate watts
p = V * I
where p = watts, I = amps, V = obviously volts.
so it looks like VA is another way to say watts.
and thanks for the VIS isolation transformer suggestion that would be a safer bet. i seen one just like it but the paint is in rougher shape on ebay.
im thinking of getting separate units an isolation transformer and the variac. i have other uses for just the isolation transformer half that i dont need the variac part for.
not sure what to do though. i should be able to plug a variac into a isolation transformer and it work safely making sure to pair the two with the same VA rating. its a little more costly though.
(This post was last modified: 10-15-2020, 12:46 PM by Link500.)
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
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