Zenith 25EC58 Restoration Thread

[vol.2]

Originally Posted by TinCanAlley

then if need be, I can use the 695 as a replacement for those other transistors?

If you show me a circuit (the schematic) with a transistor, and you give me both the original transistor and the one your are thinking about replacing it with (and their datasheets), then I can probably tell you with some confidence if it's going to work.

That's about the extent of my knowledge with this stuff; one at a time. I can't sign off on blanket replacements between transistors regardless of the use case. I'm not that good at it.

[TinCanAlley]

Originally Posted by vol.2

If you show me a circuit (the schematic) with a transistor, and you give me both the original transistor and the one your are thinking about replacing it with (and their datasheets), then I can probably tell you with some confidence if it's going to work.

That's about the extent of my knowledge with this stuff; one at a time. I can't sign off on blanket replacements between transistors regardless of the use case. I'm not that good at it.

Sounds good. I've tried to figure out which transistor package is from what year and if one is better than the other. For the 695s, I received 3 different package types, There are round white ones with black tops, black round ones that look like a water tower and the TO-92. I tried looking up the other 2, but I found no package numbers for them. I'm assuming the ones not TO-92 are earlier versions and might be of lesser quality.

The ones I'm looking at are the water tower looking one on the Horizontal module Q804 (121-447). Also, the Horizontal module is supposed to have a 121-931 (Q801), but there's a 447 in its place. Is this a suitable replacement, or is the 931 the best choice?

[vol.2]

Originally Posted by TinCanAlley

The ones I'm looking at are the water tower looking one on the Horizontal module Q804 (121-447). Also, the Horizontal module is supposed to have a 121-931 (Q801), but there's a 447 in its place. Is this a suitable replacement, or is the 931 the best choice?

Do you have the datasheets for the transistors? I looked around for them, but I can't find anything. I even went as far as doing a cross-reference on the an archived version of the NTE part cross-reference tool, but those numbers don't come at all.

I'm good enough to have an idea of which specs would be important to adhere to, but I can't tell you what the specs of the original transistor are without a datasheet.

In general though, both Q804 (waveshape) and Q801 (AFC) are not in super critical spots for either speed or gain. I would think that almost any decent modern transistor with the correct voltage requirements would do the trick. Something like a 2N4401 could work probably. Q801 would be more likely to have possible issues if the gain was too high because the AFC circuit might rely on the gain characteristics to lock in, but I can't tell you that because I don't know the gain of the original transistor.