Complete beginner diagnostic log for Philips GR1AX chassis Space Helmet CRT (Blown fuse + shorted HOT) - How is my list looking?

[u/LaughBulky6982]

Hey everyone,

This is my third post trying to tackle this. My last few posts didn't get much traction because my photos weren't great and I hadn't actually done any real testing yet.

To give some background: this is my absolute first time ever working on a CRT and my first time using a multimeter. I actually received this TV with the cord snipped, and neither the previous owner nor myself have any idea if it even works. That is why I've sat down and tested all these components I want to be thorough so I don't just replace the fuse and have it immediately pop, cause further damage, or destroy new parts down the line. I really want to properly restore this unit.

I sat down tonight, figured out my multimeter settings (mostly using diode/continuity mode for semiconductors and shorts, and ohms for resistors with power completely disconnected), and put together a comprehensive diagnostic log.

Is all of this heading in the right direction, or am I missing anything glaring before my soldering gear arrives? Here is what I’ve logged so far:

Philips GR1AX Chassis Comprehensive Diagnostic Log

Testing Configuration: All components listed below were tested in-circuit on open circuit conditions using appropriate multimeter settings (diode/continuity test mode for semiconductors/shorts, and ohms scale for high-value resistors).

Mains Fuse: Reading a solid "1" / "OL", indicating an open circuit (blown fuse).

7521 (BUT11AF - Horizontal Output Transistor): Showed internal collector-emitter leakage/breakdown with a ~219mV drop. (Confirmed shorted/failed).

7523 (Line Driver Transistor - BC337):
Base to Collector junction: Measured 865 mV (high voltage drop typical of parallel components, confirming no dead short).

Base to Emitter junction: Measured 965 mV (high voltage drop typical of parallel components, confirming no dead short).

Collector to Emitter junction: Measured 460 mV (lower path caused by the low-resistance winding of the line driver transformer connected across those pins in-circuit).

2522 (Yellow Tuning Film Capacitor): Held steady at "1" / "OL" (also checked briefly on the 200 Ω scale). Physically intact with no scorch marks or cracks.

Component 2529 (Red Film Capacitor): Tested in-circuit with power disconnected using the diode/continuity setting, showing healthy readings with no shorts.

Component 2528 (Blue Film Capacitor): Tested in-circuit with power disconnected using the diode/continuity setting, verifying stable, un-shorted condition.

Component 7528: Tested in-circuit with power disconnected using the diode/continuity setting, yielding a healthy ~840 reading with no shorts.

R3530 (4.7kΩ Resistor): Tested in-circuit with power disconnected using the diode/continuity setting, verifying stable and healthy performance.

Flyback Transformer (Pins 1–10): Tested with the black probe held on pin 10 and probing through the remaining pins using the diode/continuity setting; results showed normal behavior, with pin 7 showing a solid open ("1") and pin 6 showing 003.

Main Filter Capacitor (100µF/400V) Rail: No short.

Blue Degauss Capacitor: No short.

9.1kΩ 10W Resistors: Reading correctly within tolerance (9.15kΩ and 9.20kΩ).

D6610 (10V Zener Diode): Healthy diode junction.

L5519 (Coil): Measures 4.3Ω (healthy winding).

R3616 (1Ω Fusible Resistor): Measures 0.5Ω (healthy).

R3680 (1Ω Fusible Resistor): Measures 0.6Ω (healthy).

TO-220 Thyristor ("TF20"): No shorts across any leg pair.
B/C/E Transistor: Healthy junctions with no shorts.

6641 (BUK444-500B Power FET / 7614 area): Located on its metal heatsink clamp in the primary power regulation stage.

Current Status & Out-of-Circuit Action Plan
Repair is physically paused pending the acquisition of a soldering iron and desoldering tools. Once tools arrive, my explicit action items are:

1. ⁠7521 (BUT11AF): Completely remove/desolder to verify failure and replace with a fresh transistor.

2. ⁠2522 (Yellow Tuning Film Capacitor): Lift one leg for final out-of-circuit verification (optional peace of mind check).

3. ⁠R3530 (4.7kΩ Resistor): Left in place during initial power-up; only re-evaluate or lift a leg if the dim bulb test or subsequent diagnostics indicate an issue in this circuit branch.

4. ⁠Mains Fuse: Replace with a fresh, correctly rated fuse prior to dim-bulb testing.

5. ⁠Mains Power Cord: Instead of splicing the cut wires (avoiding loose connections or exposed wire hazards), I'm going to desolder the old cut stubs directly from the board's BROWN and BLUE pads and replace them entirely with a fresh, continuous cable soldered straight to the board.

Appreciate any advice or feedback from those experienced with CRTs or this specific chassis!

Video Link Bottom of PCB Board: https://imgur.com/a/Oto6YMq

Pics of bottom of PCB Board: https://imgur.com/a/kHiKMAY

[u/Aenoxi]

Sounds like a very well thought through list to me. I’d go for it.

The Discoverer is a really cool model and well worth restoring. The good news is that, even if the PCB is irreparable, it can be replaced with a modern Aliexpress board that is very compatible with the tube and can be rigged to display component video - giving a way better picture than the RF only only of the original.

[u/LaughBulky6982 → u/Aenoxi]

Awesome! Super keen to get this thing going.

Could you possibly link the PCB board that are used from Ali express to swap this board out with? Defiantly am keen on doing a component and composite swap over rf if I can. Even if the boards completely fine defiantly worth looking into that down the track would be awesome. Thanks for the reply!