[Foose]

Hi everyone!

i recently acquired a 118x floor model...doesnt work, speaker needs re-coned, but all in all i think its in pretty decent shape. 
i might as well be up front with the facts: i have no idea how radios actually work, and my understanding of electronics is cursory at best. 
that said, i have successfully restored a 1947 seeburg 147 jukebox, several tube amplifiers for guitar and bass, and a hammond organ, along with countless pinball machines and arcade games, so i figure this cant be all that different from anything else ive tackled before.

heres my plan so far: replace the big electrolytic caps, and the paper tubular caps, ive read the bakelite block caps are pretty much good to go so im not going to mess with them unless i need to, and then re-cone the speaker. the tubes all look like the previous owner bought them brand new, so im not too concerned with them at the moment. 

my question right now is about the paper tubular caps....these arent electrolytic, right? the parts list does not specify that they are, but then im looking at that black band around the one end of the cap that seems to always be connected to ground, so im not too sure. im also not seeing voltages marked for these caps, i was wondering if theres something im missing on the markings on the caps, or maybe i need to understand the schematic a little more in order to deduce the voltage ratings? 

theres also a mystery cap on my chassis, connected down by the 8-10 MFD and 8 MFD can caps (part 73 and 74 on my schematic) the mystery cap is a 20MFD 450v electrolytic, the positive terminal going to the first lug on that 3 lug bakelite block down there...the schematic says its a .25 MFD condenser. im thinking this was added at some point to clear up some humming as the other caps failed, but its a shot in the dark right now; i simply havent studied the schematic well enough yet.

any help you guys can give an absolute novice are greatly appreciated. ive been reading this forum for the last several days, taking in all the knowledge i can soak up, and im not too proud to admit im in way over my head. but i do love a challenge, and im a quick study, for a young buck.

thanks again,
Brian

[morzh]

Brian, welcome.

Yes you need to replace electrolytic caps, along with ALL other caps including the backelite blocks, as they are also paper caps, EXCEPT the mica molded caps.
The tubular are regular paper caps, not electrolytics.
They are non-polarized and when replaced, there's no end to be connected to GND etc.
Typically tubular all have Voltage ratings printed on them along with capacitance.
The backelite ones are all 630V rated but it is not really needed so you could get the rating according to the place in the sch, or if in doubt, 500VDC rating is vood across the board except for the line filter caps (those connected to the AC line) which have to be X or Y safety caps) and sometimes the single cap connected across the primary of the output audio transformer which sometimes is rated 1000V which is not necessary and most times 500V will do fine.

[Foose]

well i guess its a good thing i drink, smoke, and eat red meat.

so all the paper caps will get replaced....orange/brown drop or are there preferred caps for each thing? i again must apologize, im still learning.

for instance, i did not understand any of the x/y safety cap bit there. i apparently have more reading to do. but i appreciate your quick response, ive already completely fallen in love with this radio. im going to fix the crap out of this thing.

[KCMike]

Welcome. Here is a quick read about safety caps.
http://www.justradios.com/safetytips.html

[morzh]

About X/Y safety caps:

If you look at most sch, like this one

http://www.nostalgiaair.org/Resources/139/M0013139.htm

you will find a filter cap(s) - here it is #90, a pair of caps from each line to chassis, that filter noise from the AC line to keep it from screwing up reception.
Now these caps, placed across the piwer, in case of failing in the short circuit mode will create problems, from blowing up to electrocuting a person who touches the chassis if grounded himself. They later got the monicker "death cap".
Nowadays there are caps, called safety caps, that are guaranteed not to short and will always fail open. They are specifically rated in AC Volts. X-caps can be placed across the line and Y- caps - from lines to chassis.

This, for instance, is a safety X and Y rated cap.

https://www.mouser.com/Search/m_ProductD...gL_GvD_BwE

[Foose]

i had a nice read about X/Y caps this morning, i want to thank you guys for all that great information!

it makes me think back to the seeburg i restored....i had bought a cap kit for it, and there was definitely nothing in there like that....it was all brown dip caps and a couple electrolytics. i think im going to get back into that one and check it out, the schematic has a cross line cap that should brobably be changed out with an X2 if i understand it correctly.

so back to the type of capacitors to use question...are there specific replacement caps that should go with the corresponding original caps, or will the brown/orange dip caps basically work for all of them, whether they were a paper tube or bakelite block? obviously you have to change out electrolytics with electrolytics, but im not clear on the benefit of using the different types of caps they did.

thanks again everyone! cheers!

Brian

[morzh]

A cap's a cap. I like cylindrical film caps.

[Foose]

hey everyone, its been a minute!

i have ordered all my caps, and im in the process of installing them. per my usual, im testing all the resistors as i go, and realized pretty quickly that i have no idea what tolerance i should apply to any of them, or their wattage rating if i choose to replace them. ive combed the phorum, but havent really gotten too many answers from searching, so i figure id just ask directly.

as always, any help you can give would be greatly appreciated!

Brian

[Radioroslyn]

Hi Brian,
> i have no idea what tolerance i should apply to any of them
20% was pretty standard back then in radios. Test equipment is a different story, they can have 1% jobs in things like volt/ohm meters. 

> or their wattage rating if i choose to replace them.
Physical size matters most of them are going to be 1/2 watt but larger the one can be higher in wattage rating. If you are uncertain about a particular one just ask.

GL

[morzh]

Unless part of timing circuit, oscillator or calibration device, it is rarely great accuracy is needed with caps.

[Foose]

ok cool. ive got a pile of 1/2 watt resistors, but only a few 1k and 10k 1 watt and 2 watt resistors. are there any resistors that should specifically be over 1/2 watt?

thanks again, you guys rule.

Brian

[Foose]

it might be pertinent to mention all my 1/2W resistors are 350v working, 700v overload, carbon film resistors. im honestly not sure if that changes anything.

[Radioroslyn]

>any resistors that should specifically be over 1/2 watt?
#'s 61, 60, 67,and 68.  60 is a large wire wound job which acts as a bleeder for the power supply. Arran seems to have poor luck w/them being open, me not so much. 6K @ abt 20w.
61 has several sections in series. If it is a candohm style check for resistance and shorts to the chassis. Wattage between the section varies generally the lower the resistance the lower the wattage. Would take a guess and say that the largest would be abt 10w.
67 and 68 could be 1w or so.

This is with a quick look at the diagram .

[Foose]

thanks for the reply!

i havent checked my  multistage wirewound yet, but the 6500 tested pretty good. theres one or two other larger resistors im going to go ahead and replace with 1 or 2 watt resistors; theyre larger than the rest, and while im sure thats nothing to go on specifically, its probably also not bad either. 

so heres a question, and i think ive basically got the answer already, but please correct me where im wrong...

the schematic will often call out resistance values that are not what you find in the chassis. i figure that as long as the value you find in the chassis is within tolerance of whats on the print, you should be good to go. but why did they call out something on the print, and then when it came time for assembly they were like "aww heck with it, this ones pretty close!" 

i mean, im a machinist by trade, so i can appreciate and understand the meaning for having a tolerance, but this just seems a little strange that so many resistors would be off by a little here and there.

and what should i do when replacing resistors? for instance, ive got a .5 meg on the schematic, which is a 490k in the chassis. the resistor is sitting at .9 meg...obviously way too high. on my bench ive only got a 470k to put back in there, but thats still in tolerance. so do you just do that? do i bother throwing another resistor in series to try to bring it up a little, and if so, what should i shoot for, 490k or .5M? im sure the difference is negligible, but im also very new to this, so i dont know what i can get away with and what i should be obsessing over.

for that matter, what if i just put two 1meg's in parallel? would that mess up the circuit, or is that an acceptable fix for just not having the right resistor? 

thanks again for everyones help, i couldnt do this without you!

Brian

[vinzer]

The 470k or the 2 1 megs will both work ok.