What's the deal with the part numbers of the transistors in the SM? Is each transistor given a separate number though the same transistor is used in multiple locations? I've been looking at replacements to keep on hand (since they're cheap and it's better to buy more to justify shipping costs) and there are roughly 6 part numbers that correspond to a single transistor (GE-27 is an example).

Also, do the replacement part numbers for other manufactures take into account whether it's a NPN or PNP? The reason I ask is that some of the NTE part numbers note it's it one of a pair of complementary transistors. For those, is there always a complimentary transistor somewhere in the circuit?

Thanks

All the transistors with different part ##'s are different. When you sub them you are getting same or better specs. Works MOST the time.
Also case style & pin out must be watched.

OEM transistors are selected closer to the needed specs
to save $$ and best match the design.

Most the time they make an " opposite sex" twin.
They show up in audio & vert outputs on TV's sometimes.
your TV uses none of the pairs as pairs.

Some places you should only use OEM transistors.
Horz output, IF & tuners, sometimes vert & audio out,
power supply regulators. Very brand specific as to
where you can get away with subs. Sometimes OEM's
cost less. If you get a common failure you may
stock the OEM instead of going to the subs.

73 Zeno:smoke:

All the transistors with different part ##'s are different. When you sub them you are getting same or better specs. Works MOST the time.
Also case style & pin out must be watched.

OEM transistors are selected closer to the needed specs
to save $$ and best match the design.

Most the time they make an " opposite sex" twin.
They show up in audio & vert outputs on TV's sometimes.
your TV uses none of the pairs as pairs.

Some places you should only use OEM transistors.
Horz output, IF & tuners, sometimes vert & audio out,
power supply regulators. Very brand specific as to
where you can get away with subs. Sometimes OEM's
cost less. If you get a common failure you may
stock the OEM instead of going to the subs.

73 Zeno:smoke:

So even though the SM notes the part numbers from 4 different manufacturers, the specs might be slightly different than the OEM, but is supposed to work. Just a matter of trial and error.

I found a place that has about 60% of the ones I'm looking for of NOS Zenith parts. I think I'll grab those and start a hunt for more places.

Thanks for the info.

Is there a brand of resistors recommended for replacements? I've run across a couple of them that aren't listed in the SM. They're noted in the pics and have an arrow pointed to them, but are not on the resistor list. I'm going to be doing some testing of them and figured I'd better get ready for replacements. I found many OEM Zenith ones online, but there are a number of them I can't find. So if I have to order from Mouser or such, which brand is recommended be those here?

An example of one I can't find is noted in Photofacts as R202 and noted on the schematics as just a 33K resistor and not on the parts list in the back of the SM. I found it on the underside and matched up the color bands, so I know it's a 33K 10% and is the only one. Being the only one I can't get the Zenith part number from another on the list.

Thanks

Is there a brand of resistors recommended for replacements? I've run across a couple of them that aren't listed in the SM. They're noted in the pics and have an arrow pointed to them, but are not on the resistor list. I'm going to be doing some testing of them and figured I'd better get ready for replacements. I found many OEM Zenith ones online, but there are a number of them I can't find. So if I have to order from Mouser or such, which brand is recommended be those here?

An example of one I can't find is noted in Photofacts as R202 and noted on the schematics as just a 33K resistor and not on the parts list in the back of the SM. I found it on the underside and matched up the color bands, so I know it's a 33K 10% and is the only one. Being the only one I can't get the Zenith part number from another on the list.

Thanks
Photofact doesnt list common carbon resistors. You may be able to
find an old resistor kit or someones old resistor box. For new ones
just use the newer flameproof ones. Smaller & more reliable.
Only other caution on resistors is DO NOT replace carbons with
wire wounds. You are putting a coil in the circuit & it can
really throw off some circuits.

73 Zeno:smoke:

Photofact doesnt list common carbon resistors. You may be able to
find an old resistor kit or someones old resistor box. For new ones
just use the newer flameproof ones. Smaller & more reliable.
Only other caution on resistors is DO NOT replace carbons with
wire wounds. You are putting a coil in the circuit & it can
really throw off some circuits.

73 Zeno:smoke:

I've been looking at metal film. Are these okay? They're film and not wire wound.

If I can find the values by the stripes, how do I figure out the wattage? I figure I'll play it safe and get 1w for all unknown. I figured that the wattage was like the voltage on caps. You can go up, but not down. I also ordered all 5% as I figured it would vary less than a 10% and this wouldn't affect the circuit.

I would stick with the original wattage, they act like fuses as well, better to burn up a resistor when something shorts than a hard to find component.

most resistors used are 1/2 watt, once you get used to them you can usually identify the wattage of a standard carbon resistor by how big they are.

In most cases anything over two watts is going to be a wirewound.

Photofact doesnt list common carbon resistors.

Really? I sure see a lot of them listed. In fact, I don't see any where they are not listed in the Photofacts currently sitting on my desk.

An example of one I can't find is noted in Photofacts as R202 and noted on the schematics as just a 33K resistor and not on the parts list in the back of the SM. I found it on the underside and matched up the color bands, so I know it's a 33K 10% and is the only one. Being the only one I can't get the Zenith part number from another on the list.Which Photofact are you referencing?

Which Photofact are you referencing?

It's Photofacts 1370-2n. If you look at page 16 you'll see parts identified via arrows on a picture of the underside of the chassis. On that page you'll find R202, R203 and R207 (all of which I've verified as being on my chassis). When you go to page 22 where the resistors are listed, it jumps from R201 to R206 and jumps again to R227. Quite a few have been skipped.

It's Photofacts 1370-2n. If you look at page 16 you'll see parts identified via arrows on a picture of the underside of the chassis. On that page you'll find R202, R203 and R207 (all of which I've verified as being on my chassis). When you go to page 22 where the resistors are listed, it jumps from R201 to R206 and jumps again to R227. Quite a few have been skipped.

Apparently Photofacts made a change at some point to list only the "Power & Special" resistors according to the heading on page 22. I was not aware of that because I rarely ever work with Photofacts on equipment that new. The schematic page does state that all resistors shown (unless otherwise marked) as being 1/2 watt or less. No need to use 1 watters.

Really? I sure see a lot of them listed. In fact, I don't see any where they are not listed in the Photofacts currently sitting on my desk.

Per my immediately prior post, I see that at some point Sam's started listing only the "Power & Special" resistors. That's quite a change from the earlier Photofacts where they even listed the color-code for each resistor. (sample below)

http://img28.imageshack.us/img28/9147/rwam.jpg (http://img28.imageshack.us/i/rwam.jpg/)

Apparently Photofacts made a change at some point to list only the "Power & Special" resistors according to the heading on page 22. I was not aware of that because I rarely ever work with Photofacts on equipment that new. The schematic page does state that all resistors shown (unless otherwise marked) as being 1/2 watt or less. No need to use 1 watters.

So, basically, if it's only noted by value I should replace it with a 5% 1/2 watt? I don't think I'd be able to tell the wattage, so the 1/2 watt 5% would cover just about all of them.

So, basically, if it's only noted by value I should replace it with a 5% 1/2 watt? I don't think I'd be able to tell the wattage, so the 1/2 watt 5% would cover just about all of them.Yes, 1/2 watt unless otherwise noted. The originals were 10% & 20% tolerance, but 5% tolerance resistors are now available without the large cost premium they had in years past.

Yes, 1/2 watt unless otherwise noted. The originals were 10% & 20% tolerance, but 5% tolerance resistors are now available without the large cost premium they had in years past.

Sure wish there was a local place that had the selection of Mouser. Still, I usually get my stuff in 4 days.

Thanks!

Metal film is fine. On a SS set there is some risk going
with higher watt resistors. In some cases like the 330 ohm
on your 9-57 ( also on 9-90 ) board need to go from 1/2
up to 1w due to a near 100% failure rate. One place you
should never go up is low value resistors. They are often
used as a fuse only. Newer sets use a lot of them.

73 Zeno:smoke:

Metal film is fine. On a SS set there is some risk going
with higher watt resistors. In some cases like the 330 ohm
on your 9-57 ( also on 9-90 ) board need to go from 1/2
up to 1w due to a near 100% failure rate. One place you
should never go up is low value resistors. They are often
used as a fuse only. Newer sets use a lot of them.

73 Zeno:smoke:

I wish there were a way to know if it's a 1/4 or 1/2 just by looking. If a low value might be used as a fuse, they should note the wattage. As it is, the schematics only state that they are 1/2 or less unless noted. Well that doesn't do much to help if the resistor is meant to be no higher than a 1/4.

So is there some kind of guideline with regards to resistor value and wattage? Is there a certain value where anything at or below it is usually a 1/4 and anything above it goes to 1/2 and more as the value increases? Or is value independent of the heat it dissipates?

Must admit I'm learning lots lately. Once I get the Avanti up and fully functional, I'm taking what I've learned and giving the 19JC55Z chassis at thorough going over as well.