Hi fellow enthusiasts,
Re-capping a 589 Grunow and am a bit confused.
On looking at the electolitics, it appears that there are only 2 of these.
I will be replacing them both with 22's.
Upon looking at the wiring of these 2 cans(which have been replaced before), I notice that one of the cans has 2 leads.
I figured the one that goes to the can leg(twisty type lug to secure can)would be a ground. Upon following the wire, I found that it goes to a terminal strip on the other side of the chassis.
It is not a ground wire. Did a continuity test with my ohm meter to verify this.
Could one of you guy's that is schematic savy take a look at the schematic and enlighten me?
I am not too good on schematics yet, so I am guessing.
I am more of a parts swaping geek. Can do that, but have a hard time with schematics.
That is on my to do list for sure.
Absolute blast working on these old timers. They are all so different.
murf
Can you post link or image of schematic? I for one will have a look.
There are two types of cans with more than one insulated terminal.
One is where one is plus and another is minus, and the can is unconnected.
Another is (and this is probably what you have) where the can is minus and all the insulated terminals are plusses, so there is more than one capacitor inside with all the minuses combined and connected to the can.
You can see how it was secured to the chassis: if it is with a clamp that hugs the can withouut any insulation and connects directly to the chassis, the can is the chassis then.
If the clamp has an insulation between itself and the can, usually a piece of dense insulating paper, then the wire connected to the can probably goes elsewhere and not to the chassis.
Often times that wire goes to a large wire-wound bias resistor that creates some negative bias low voltages between the most negative point of the schematic (the neg. output of the rectifier, like sometimes it is the centertap of the respective winding of the power tranny) and the chassis. This is one case where the chassis connects to a capacitor's plus and not minus as in most cases.
One of your electrolytics negative side does not go to chassis ground. The terminal strip should connect this negative lead to the HV center tap, the field coil, and R13, which is a 560K resistor. If it is the positive lead, it should connect it to the filament of your rectifier, G2 of your output tube and to the primary side of your output transformer. (Also other places but this gives you an idea....)
Since you only have two electrolytics present and the schematic only lists two of them, willing to bet one is positive and the other is negative lead of cap.
Have you examined the body of the cap to see if it lists what the leads are?
Murf
It is fairly simple.
Both caps have their positives together, at the output of the rectifier tube.
Both caps are singles, judging by the sch. So if you have one that is dual then one half is propbably is not used.
Now, it does not matter as you need to replace them, so no matter how you will stuff your caps, you should have two caps, each one having one positive and one negative.
Again, both will have their positives topgether and connnected to the 80 tube's filament, the rectifier positive output.
Now, one negative from the cap #60, 10uF, goes directly to GND (chassis).
Another negative, from the cap #61, goes to the field coil, through which it connects to the GND and the coil's resistance forms the negative bias used in the output amp. This is where that mistery wire of yours went, and if you buzz it to the chassis, you will see a typical field resistance, which I cannot find but I can figure it is anywhere from 1Kohm to 3kOhms.
Ok, thanks guy's.
Just wanted to clarify with the experts.
Have a great weekend.
Have it playing now, but the volume is not what it should be.
Pulls in the stations fine.
Tubes seem ok.
Re-capped with new electrolitics.
Resistors?
I noticed the 2 larger dogbone resistors(6k and 20k) are checking a little over the 20%.
Kind of a pain to check them seeing as you really need to de-solder one end to get an accurate reading.
Easier just to replace them.
I will replace the dogbones with 2 watt resistors.
murf
It's very easy to get the filter cap wiring mixed up on one of these early to mid 1930s sets if you aren't careful. Not only did they used to use different grounding points for each cap sometimes they had the positive side tied together with the speaker field coil on the negative side. In some cases they would have a single cap in one can and a two or more section cap in the other, the Rogers Ten-60 I am working on was wired this way. Many time the innards of the filter can had no connection to the can itself.
With regard to the resistors you can usually test them in place, unless that resistor happens to be connected in parallel with a coil or another resistor. When it comes to replacement if they are within 20% or better of what they are supposed to be I leave them, with the exception of ones that are normally buried and inaccessible without tearing the radio apart, like some of the ones are in my Rogers Ten-60. If the volume is low one common think that can fail is the plate resistor on the first audio tube, sometimes they used a 1/4 Watt where they should have used a 1/2 Watt.
Regards
Arran
Thanks for the info.
I will check it out this weekend.
I think the filter caps are in right.
Seems to play fine, just not enough volume.
murf