I am sitting here trying to recap a Coronado 3128. It is a cramped little beast but I have done all but the Ecaps. There is a cardboard box with the 3 Ecaps at 4, 4, and 12Mfd. The problem is that I dont know where the wires go. They are color coded but nothing on the Schematic:
Then there is this weird big flat thing that I can only guess is an Ecap too. I really dont think it is original since it only fits above the chassis and has electrical tape connecting the wires. Any ideas on that?
Oh and should I replace that big chinese cap or is it new enough?
Working on it again. I have the + of the 12 and the + of the first 4 going to pin 4 of the 25z5. I have the + of the second 4 going to pin 3 of the 25Z5.
I do not know where the rest go. One of the wires that was connected to the wax box goes to pin 2 of the 43 tube. The other goes to a meeting point on the IF? (the large metal box on the bottom)
As for that big fat flat Ecap it does have numbers on it. they are 312392. The first wire goes to the same meeting point on the metal box (IF). The second wire goes to a 1. uf a .1 uf and then they are connected to pin 3 of the 25Z5.
Did someone mess with this? Maybe they bypassed Ecap instead of replacing it...?
Connect - leads from a 4mf and a 12mf. Connect that to the off/on switch, the side that doesn't have the line cord connected to it.
Connect the - of the second 4mf to L-9 the side that isn't connected the the off/on switch.
Pin 2 of the 43 is the plate pin. The only thing connected to it is the .015 C-17 and one leg of the primary of the output transformer.
Where the two + of the 12 and 4mf that goes over to the IF can.
I'm not seeing a 1.mf cap in the diagram. The .1 is C-19 goes from pin 2 of the 25Z5 to the cold side of the off/on switch.
Terry
(This post was last modified: 06-30-2015, 02:59 PM by Radioroslyn.)
Well,
I just dont know... That is not where the wires are going and the big chinese cap is a 1.. Someone must have done something under the chassis and I ant figure it out
I dont know what the cold side is and there are 4 tabs coming off of the switch. Now I notice I dont have any 12uf Ecaps.. Only 10 and 22... UGH!
22 is better than 12 you know. they will work fine. Cold side of the off/on switch. Turn the set off. Use your ohm meter and measure the resistance from each of pin on the AC plug to the off/on switch one terminal at a time. The one which shows continuity to the off/on switch is NOT one to connect the - side of the two filters. Use the other switch terminal. This is B-.
To put simply what we are trying to find is which side of the off/on switch is connect to the power cord. One side of the cord is connected to the switch and the other side of the cord is connected to pins 2 and 5 of the 25Z5. The - side of the filters connect to the side of the switch that is NOT connect to the cord.
Terry
You know I'm lisdexsic
(This post was last modified: 07-01-2015, 06:53 AM by Radioroslyn.)
No Kirk;
In this case you are not the dumb one, whomever designed this thing was the dumb one, or crazy. At first glance I thought that maybe they had used the 25Z5 for a voltage doubler, but no, one diode does absolutely nothing but power the field coil for the speaker. In most of these early AC/DC sets they connected both of the diodes in the 25Z5/25Z6s together in parallel.
Now you would think, hmm, AC/DC set, department store set, so cheap set, but these clowns added an extra filter choke doing what could be done with the field coil on the speaker. I can only speculate as to why they did this? A trainload of speakers for DC only sets that had no hum bucker? A rail car full of filter chokes they had to use up? Patent royalty circumvention?
In any event filter cap C20A and C20B and paper cap C19, one end of the speaker field coil, and one end of that filter choke are all connected to the same place electrically, to the switched side of the power line which is B-. Capacitor C20C is connected to the other end of that filter choke, which is connected to the common negative for the rest of the set.
Regards
Arran
same case for me, the first time I looked at it, I thought it was a Delon doubler, and the schematic drawing is PITA to read, all garbled, and I was about to make a fool of myself by writing a comment to that effect, when something caught my eye and told me to take another look....nope, no multiplier, just a separate field coil rectifier and filtered ground. Ug-lee.
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