Zenith 10-H-571 "Spinet" - Printable Version
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RE: Zenith 10-H-571 "Spinet" - morzh - 01-12-2017
This is what a schematic readability costs me: since I cannot read all the designators on the sch, I simply ordered every item qty 10, which is especially expensive when ordering capacitors as they are about a $1/pc. Instead of ordering the exact numbers. This brought the total order to $140 whereas it'd be more like $40 otherwise.
But then again, I prefer to have a stash of parts available for the future so no regrets.
[Video: https://www.youtube.com/watch?v=Q3Kvu6Kgp88]
RE: Zenith 10-H-571 "Spinet" - Eliot Ness - 01-12-2017
(01-12-2017, 11:24 AM)morzh Wrote: .....This brought the total order to $140 whereas it'd be more like $40 otherwise. But then again, I prefer to have a stash of parts available for the future so no regrets.
We used to go to hamfests and buy up epoxy capacitors by the box load.... at the end of the day we'd divide them up by handfuls. I also used to buy new Sprague Orange Drops by the hundreds from a supplier up in Cincinnati or Dayton and then we'd divide those up too. Saved a lot of money that way and I still have a pretty good stock of caps for sets from around the 30's.
I did have to place an order with Mouser recently for all of the electrolytic caps in my Royal 7000 Transoceanic that I hope to get to pretty soon.
Looks like all of those paper caps are original so it'll look nice if you decide to restuff them. I was looking for some brown hot glue sticks yesterday but couldn't find any.... they used to be easy to find. I did buy some that are amber colored made for wood that won't look too bad restuffing paper caps. Looks like I'll need to hit Amazon or eBay if those aren't dark enough.
RE: Zenith 10-H-571 "Spinet" - morzh - 01-12-2017
The regular white glue does not look bad. Yes brown would look better but .....
There's been no restoration done on this radio so everything is factory at this point. The rubber-coated wires included
RE: Zenith 10-H-571 "Spinet" - TV MAN - 01-12-2017
That is sure a lot of caps under thar. You sure that isn't a TV?
I bet if you squint real hard you can see a picture tube over there. I sure don't envy you. Got an RCA that's about like that, and it IS a TV. I sure will like to see how she turns out. Have fun!
RE: Zenith 10-H-571 "Spinet" - morzh - 01-12-2017
This is all due to the FM circuitry.
Not bad, "I've seen woise" © Miracle Max.
RE: Zenith 10-H-571 "Spinet" - Arran - 01-13-2017
(01-10-2017, 10:04 AM)morzh Wrote: OK, yesterday I res-stuffed the first tubular guy and took out the twist-lock cap.
The twist-lock, as it's been the case with the previous Zenith cap, in fact shows that it is not dry. It should be 5uF, and two 15uF caps, 300V and 250 and 450V. The capacitances are 8uF, 18uF and 30uF. Considering it is 40-s, and not 30-s.....
I am tempted to reform it and see how it behaves.
I need to order a bunch of the caps, like 0.1uF. I could use 0.15uF I have but as the sch is barely readable when it comes to ref designators I cannot quite see which cap goes where and so though I am sure in some places they can be used, in some others it is possible 0.1uF is preferred. If only I could have a nice readable schematic with ref designators showing clearly.Oh well, can't have it all at once.
On the other hand, this murkiness is more pronounced on the Beitman's and only in printed form, the first PDF Nathan gave is kinda readable. And yes, some of those caps should be what they are although 0.15uF would work too. Like those in teh detector circuit in the feedback bypass.
Mike;
I've run across that myself with the old twist lock style condenser cans, I once repaired a DeForest-Crosley of the same age as your Zenith, as well as a few Canadian RCA and G.E sets with the same, and whilst they appeared to be good since the set still played with them in place I don't trust them. If they were from the 1960s or 70s I might roll the dice on reforming, but not on ones made before Pearl Harbor.
I would just order some .1 uf 630vs, it's a standard size so any amount you order you will end up using at a later date on something else. That's one of the sizes I can confidently order in quantity to get a bulk discount, much like .01s, .005s, and .047s, it's like 90% of the tube type radios, TVs, and amps use at least some of them.
Regards
Arran
RE: Zenith 10-H-571 "Spinet" - morzh - 01-13-2017
Arran
yes, this is what I ended up doing; ordered an excess number of caps from Mouser. Good caps are expensive, I ordered the Vishay with 630VDC/220VAC rating tubular, this one:
http://www.mouser.com/Search/ProductDetail.aspx?R=MKT1813410635virtualkey61310000virtualkey75-MKT1813410635
and it is $1.28/pc.
I am sure there are cheaper ones but not from Mouser. Another plus of these: they are large and come with sturdy long leads which helps. As for those caps some suppliers sell, no-name or names unknown to me, I simply do not trust.
As for the twist lock, like I wrote above, found corrosion inside as it was not reforming well. You can always tell by how the reforming current behaves, whether the cap is improving or not. I restuffed it and I did not quite follow the values as from the sch the 5uF can be replaced with 12uF, 15uF 450V - with 20uF (it is not the first rectifier filter cap so the value is not critical if it is larger), and the 15uF 250V - also can be 12uF without any ill effects.
The first 30uF rectifier cap - I found two solutions, the Nichicon high ripple cap that provides about 500mA ripple, which is not bad, and then I decided to go with two 68uF caps in series that will afford almost 800mA ripple. I hope they fit in the can, I think they should. I almost always do this when restuffing the first cap in all my larger radios; with smaller ones I use a single high ripple cap solution. I use full voltage rating or close on each cap: this gives me two advantages: 1) no leakage equalizing resistors needed, and 2) higher voltage dictates higher ripple rating.
Basically if the old rectifiers did not rely on the capacitance size to determine the magnitude of the output voltage and the rectifier tubes itself did not limit the output cap size, I would simply use 100uF high ripple across the board, those have more than enough ripple rating, but unfortunately it s not the case and one has to be crafty with these to balance between the size, ripple rating and the needed capacitance, as today's caps simply smaller than those from the days of yore.
RE: Zenith 10-H-571 "Spinet" - Phlogiston - 01-13-2017
Guys, I find this series of replacement caps very useful in restuffing original cans - when I absolutely have to use an electrolytic. I keep values up to 82uf/450V in stock.
http://www.mouser.com/ProductDetail/Nichicon/UCS2W220MHD/?qs=sGAEpiMZZMtZ1n0r9vR22cDNKFDu5zhSu12iRXz3wlg%3d
My personal feeling on "reforming" old caps is - - - never.
RE: Zenith 10-H-571 "Spinet" - Arran - 01-14-2017
(01-13-2017, 10:22 AM)morzh Wrote: Arran
yes, this is what I ended up doing; ordered an excess number of caps from Mouser. Good caps are expensive, I ordered the Vishay with 630VDC/220VAC rating tubular, this one:
http://www.mouser.com/Search/ProductDetail.aspx?R=MKT1813410635virtualkey61310000virtualkey75-MKT1813410635
and it is $1.28/pc.
I am sure there are cheaper ones but not from Mouser. Another plus of these: they are large and come with sturdy long leads which helps. As for those caps some suppliers sell, no-name or names unknown to me, I simply do not trust.
As for the twist lock, like I wrote above, found corrosion inside as it was not reforming well. You can always tell by how the reforming current behaves, whether the cap is improving or not. I restuffed it and I did not quite follow the values as from the sch the 5uF can be replaced with 12uF, 15uF 450V - with 20uF (it is not the first rectifier filter cap so the value is not critical if it is larger), and the 15uF 250V - also can be 12uF without any ill effects.
The first 30uF rectifier cap - I found two solutions, the Nichicon high ripple cap that provides about 500mA ripple, which is not bad, and then I decided to go with two 68uF caps in series that will afford almost 800mA ripple. I hope they fit in the can, I think they should. I almost always do this when restuffing the first cap in all my larger radios; with smaller ones I use a single high ripple cap solution. I use full voltage rating or close on each cap: this gives me two advantages: 1) no leakage equalizing resistors needed, and 2) higher voltage dictates higher ripple rating.
Basically if the old rectifiers did not rely on the capacitance size to determine the magnitude of the output voltage and the rectifier tubes itself did not limit the output cap size, I would simply use 100uF high ripple across the board, those have more than enough ripple rating, but unfortunately it s not the case and one has to be crafty with these to balance between the size, ripple rating and the needed capacitance, as today's caps simply smaller than those from the days of yore.
Mike;
For replacing paper caps I use the ones from WJOE radio, which are semi generic, they have the brand name of some Taiwan company, but I always put them through my EICO resistance-capacitance bridge tester and test them at high voltage first, I haven't found a bad one so far. I have bought some from Radiodaze before, with those you sometimes get a no name cap but in other instances they sent me Mallory brand caps which have an "M" with a horizontal line through it. If you don't mind radial lead caps Panasonics are pretty good, they have a new series of large value film caps, with a built in fuse feature, which could be useful for early AC sets like a Philco 20 or an RCA Radiola 18 that used large paper caps as filters.
There seems to be a difference of opinion about adding equalizing resistors when running electrolytic caps in series, in some books they suggest this but Allan Douglas cited some material that suggested it as being unnecessary, at least with modern electrolytics. Perhaps the manufacturing tolerances are better now, which would make some sense. I've used old photoflash capacitors salvaged out of disposable cameras and they didn't seem to mind being connected in series without the resistors, they were 330 VDC though, and usually of the Rubicon brand.
From my understanding the value of the input capacitor is what is supposed to matter in terms of size, at least with rectifier tubes like a #80 and their octal descendents, the output side is not supposed to matter. It's something I didn't really observe in the past, I used those same photoflash capacitors in series and some were 160 uf as singles, it didn't seem to make much difference in the B+ voltage, or in the life of the rectifier, but then again these almost always had a field coil on the other side as a choke. In AC/DC sets I often used the 160 uf straight on off the 35Z5/35W4, same story, and many of the sets I did this with were used as "Daily Drivers". I wonder if this is related to the fact that they are intended to be used in camera flashes, in that they are supposed to charge quickly from a cheap inverter supply powered by a AA cell, or just the fact that they are electrolytics of a more modern design and formulation?
Regards
Arran
RE: Zenith 10-H-571 "Spinet" - Mondial - 01-14-2017
Arran, a lot depends on the series resistance of the power transformer secondary winding.
The main limitation of the rectifier tube is its repetitive peak current rating. As you increase the capacitance of the first filter, the rectifier conducts a higher peak current for a shorter portion of the AC cycle waveform. If the transformer winding series resistance is very low this peak current can exceed the tube's maximum rating. In this instance, the rectifier only conducts at the very peak of the AC waveform and the DC output approaches the peak AC voltage (1.41 Vrms)
If the transformer has a high winding resistance, then the size of the cap doesn't make much difference because the rectifier peak current is limited by the series resistance. Under load, the cap voltage never reaches the peak AC voltage and conducts for a greater portion of the cycle, resulting in a lower DC output voltage. With a larger first filter capacitance the DC output voltage will not change much, but the ripple voltage will be reduced.
RE: Zenith 10-H-571 "Spinet" - morzh - 01-14-2017
Took the rebuilt cap, checked it quickly for functionality...one section's shorted. Opened it up after it was all glued together, no short and no good explanation as to why. I just resoldered the section, reinsulated, closed and glued the cap. Now it was fine, so I put it back in the chassis.
RE: Zenith 10-H-571 "Spinet" - Paul Philco322 - 01-14-2017
Mike if you came to Plymouth you could have called me for a Guinness. You come up here again tell me!
Paul
RE: Zenith 10-H-571 "Spinet" - morzh - 01-14-2017
I sure will, Paul, I sure will. I might even have some with me.
RE: Zenith 10-H-571 "Spinet" - morzh - 01-23-2017
The recap is somewhat of a PITA. Yes there is enough space, but the way the caps are soldered, couple with rubber-coated wiring, almost every time I re-stuff a cap, there are wires to be replaced and I have to do that before putting the cap back. Or some resistors to be changed also before the cap is put back.
So it is not moving at the pace I was hoping it would be.
But it is chugging along.
RE: Zenith 10-H-571 "Spinet" - Eliot Ness - 01-23-2017
The FM sure did mess you up space wise, and those rubber covered wires are always a PIA.
Are you using a heat gun to gut the Zenith capacitors?