I am currently restoring a Predicta Holiday, and am having trouble resolving an issue with "no picture, no sound". I have a faint raster, and an audio hum (hum decreases at full CW on the volume control).
I have reviewed a similar thread on Videokarma, but that has not helped (yet).
Here is what I have done so far:
- Tested all tubes
- Re-capped all electrolytics
- Re-capped the chassis
- Replaced the rectifier diodes and caps
- Replaced R77 with individual resistors (13 ohm, 18 ohm, 8 ohm)
- Replaced R76 with two SL12's
- Replaced R78 "fusistor" with a 5.6 ohm 10W resistor and a 1A fuse
- Re-capped the main board, replaced all networks and the 12CA5 (someone has replaced the socket)
- Corrected a cold solder joint in the tuner filament connector pin
- Removed a solder bridge from the 2nd IF (shorting C14 and R15) , replaced some resistors, and replaced the 5AM8
- Verified resistance values in the fly-back and L23 (okay)
- Replaced resistors R66, R67, R70, and R71 in the Width/Boost circuit
- Checked R5 (Width) and R68; measure okay

Using Sam's as a reference, here are my voltages:
- Cathode of M1: 275V vs. 290V
- 280V Source: 262V
- 260V A Source: 257V
- 260V B Tuner B+: 239V
- 260V C Source: 238V
- 140V Source: 144V
- 435V Boost: 391V at pin 1 of the CRT ( R5 full CCW; 350V centered); voltage seems to decay slowly

I would certainly appreciate some insight...

Do you have any test equipment that you can use to inject video and or IF signals (also a power isolation transformer to keep the hot chassis from frying your test equipment)?

The voltages mostly look within reasonable tolerance (in tube equipment a 20-30% B+ and general voltage reading tolerance is not unreasonable).

Thank you for responding.

I have a B&K Isolation Transformer, and a B&K Model 1077 Television Analyst. I have injected an RF signal at the antenna terminals (nothing). I have input an IF signal at the 3rd IF amp (very faint, fuzzy test pattern outline, no sound). I repeated this at the 2nd and 1st IF amps, with the same results.

I thought maybe the low 435V Boost might be part of the dim raster issue, but I can't seem to correct it.

I just re-ran the 3rd IF test, and have an audio tone. I adjusted the Horizontal Range, Height, and Vertical Lin controls, and have an image! A bit distorted though (pulled down from the top,etc). I have attached an image (sorry for the glare). I re-ran the RF test, and still no sound or picture. Maybe the tuner. I will re-run the 2nd and 1st IF tests.

Re-ran the 2nd and 1st IF tests. Still get an image and tone. The picture is still pulled down from the top. The vertical centering magnet doesn't seem to help.

Have you or the previous owner tested the CRT?

Vertical linearit is off. Do the vert linearity and height controls have an effect? One or both made be concentric controls on the side you need a screw driver to get at.

Thank you for helping with this.

I have not yet put the CRT on my B&K 465 tester/restorer. The previous owner said the CRT has an open grid 2. I wanted to test it with the restored chassis first. I will test the CRT.

The vertical linearity and height controls do have an effect. I have worked to balance those, as well as the vertical hold. When I adjust the linearity, the vertical rolls, so I have to go back and forth. I have been able to improve the vertical linearity and width a bit, and now it is over-scanning a bit vertically.

Some new clues:
- When I turn the Horizontal Hold CCW, the screen goes dark.
- I was able to get an RF signal through the tuner. This was by accident, as I had the tuner on Ch 3, and switched the B&K 1077 channel to 2. Maybe tuner alignment.

Before you go off trying to align the tuner, check the fine tuning mechanism closely. Many fine tuning adjustments can get you a complete channel off, particularly if their mechanical mechanism for connection with the fine tuning knob is off.

If that's a wafer type tuner, be sure all the wafer rotors are turning solidly with the shaft with no slop or play. Sometimes a a rotor will even be stripped at the hub and not turning at all.

Thank you.

I'll take a closer look at the tuner, and fine tuning.

CRT emissions test "bad", although I have an image.

The tuner rotors are all working properly. The fine tuning mechanism seems to be in order as well. Can't find any cold solder joints. Tubes test okay. Kind of stumped.

Check that the coax from the tuner to the IF board is making good contact

Thank you all for your suggestions!

I removed and cleaned the tuner, including the fine tuning capacitor plate. Checked for cold solder joints, etc. None found. Re-installed the tuner, making sure I had good contact from the coax connector to the IF board. Put an RF signal from my B&K 1077 through the tuner, and have sound and an image! Put a signal from my DVD player through the tuner (on channel 3), and have a decent picture and sound! The picture is faint, probably due to my CRT being very weak.

Still making some tweaks. The sound still is low, and has a significant buzz. The buzz pot doesn't help much. Sometimes the picture rolls and jitters when scenes change.

Is anyone willing to part with a 21FDP4 or 21DAP4 CRT?

I also need a fine tuning knob.

Again, thank you for your help!

Forgot to mention that I also replaced the 5X8 in the tuner. The old tube read "good", but the replacement has a higher output. May have made a difference.

Managed to find a decent CRT replacement, and to get the controls (touchy), adjusted pretty well.

I had an annoying audio hum, until I tapped the L16 (Sam's) 2nd sound IF coil 32-4745-2 with my small plastic tuning screwdriver. The sound cleared!

Now, when I slightly wiggle the coil shield, the hum cuts in and out.

I have removed the board (again), and have checked for cold solder joints, etc.

Everything looks clean.

Do these coils have a history of internal intermittents?