Duncan's 1960 Magnavox - Videokarma.org TV - Video

Electronic M · #1 08-08-2024, 02:10 AM

Unlikely C2 damaged the output tube, but R50 that JR Tech mentioned could easily have been damaged if there was excessive leakage or shorts on that section of C2.

Mr.Duncan · #2 08-08-2024, 08:44 AM

Quote:

Originally Posted by Electronic M

Unlikely C2 damaged the output tube, but R50 that JR Tech mentioned could easily have been damaged if there was excessive leakage or shorts on that section of C2.

I agree, so far R50 and R51 tested fine. But I may replace them just incase.

R50: Measured 232. Spec is 220
R51: Measured 328 Spec is 330

MuzzcoVW · #3 08-09-2024, 08:55 AM

I'm really enjoying following your journey here. That set is a copy of a unit I was looking at in NY state... but was about $2000 overpriced. I'll be following along as I begin the recap of my Silvertone this weekend. What CRT does that use? It's the same size as my Silvertone. Oh, and someone said they wished they had an electronics parts hous like that nearby... same here!

Mr.Duncan · #4 08-09-2024, 10:40 AM

Quote:

Originally Posted by MuzzcoVW

I'm really enjoying following your journey here. That set is a copy of a unit I was looking at in NY state... but was about $2000 overpriced. I'll be following along as I begin the recap of my Silvertone this weekend. What CRT does that use? It's the same size as my Silvertone. Oh, and someone said they wished they had an electronics parts hous like that nearby... same here!

Thank You!

This one uses a 24AHP4 tube.

old_tv_nut · #5 08-09-2024, 10:30 AM

Quote:

Originally Posted by Mr.Duncan

I agree, so far R50 and R51 tested fine. But I may replace them just incase.

R50: Measured 232. Spec is 220
R51: Measured 328 Spec is 330

In my opinion, replacing common resistors that are in spec "just because" is a waste of time if you have operational problems that you need to get fixed, unlike certain capacitors that could be eventual failure points.
Did you know that 10% or 20% carbon composition resistors were often near the plus or minus limit of value because the production line output of a particular value covers the whole range of +/- 20% and then the 5% parts are selected, and then the 10% parts are selected from the remainder, and then the over 20% parts are culled from the final remainder? So old tube-era sets were expected to have resistors that are towards the ends of the spec and still work. The time to replace resistors "just because" is after all the real problems are fixed.

Mr.Duncan · #6 08-09-2024, 10:51 AM

Quote:

Originally Posted by old_tv_nut

In my opinion, replacing common resistors that are in spec "just because" is a waste of time if you have operational problems that you need to get fixed, unlike certain capacitors that could be eventual failure points.
Did you know that 10% or 20% carbon composition resistors were often near the plus or minus limit of value because the production line output of a particular value covers the whole range of +/- 20% and then the 5% parts are selected, and then the 10% parts are selected from the remainder, and then the over 20% parts are culled from the final remainder? So old tube-era sets were expected to have resistors that are towards the ends of the spec and still work. The time to replace resistors "just because" is after all the real problems are fixed.

I think I may go that route "just because" once I solve the vertical circuit problem. I'm still struggling to find the error, so far all replacement capacitors are wired correctly & test correct.

When able, I've been buying higher spec replacement parts.

For example if it called for a 20% +/- tolerance I'd replace it with a 10% tolerance part capacitor. (plus slightly higher voltage rated capacitors 400 vs 630.)

As for resistors, that does make sense!

If we look at R50 for example, it should be 220 ohm @ 1watt.

Does anyone have a recommendation of what TYPE to buy?

When looking at that spec resistor with a 1% tolerance rating I have Wirewound vs Metal Film.

If I go to 5% tolerance "Metal Oxide Film" shows up.

What's best? - I really don't mind paying extra for higher quality / better parts.

options by Thomas Duncan, on Flickr