Need to stock up on parts?
From John Stortz ... here are some always timely tips!
--------- Stortz's Top Ten Rules of Parts ----------
Stortz's rule of parts #1: If you have a part fail once, it is likely to fail again, so order an extra one whenever possible. Next time, you will be the hero for getting the thing back on the air fast.
Stortz's rule of parts #2: Keep all unique spare parts for a specific unit in a larger box, clearly labeled as to what equipment they belong.
Stortz's rule of parts #3: Label all used parts to indicate if they were working when removed, or if something is defective, or if pieces have been removed. If a component is being saved to take pieces to repair another unit, mark it on the label.
Stortz's rule of parts #4: Each critical fuse should have a box of small fuses [of the correct size] right next to the fuse holder, attached by Velcro, for quick access. This makes them easy to locate in an emergency.
Stortz's rule of parts #5: If you can, buy generic. [ A warning, though: all parts are not equal in quality or tolerance. Be especially careful about generic substitutions in critical, close-tolerance or matched-pair situations]
Stortz's rule of parts #6: When ordering generic parts, try to replace components with ones that have higher voltage ratings [capacitors, lamps, diode PRV], higher current ratings [diodes, relays, wires, switches ...], higher wattage rating [resistors, potentiometers, zeners, transistors, SCRs, transformers etc].
Stortz's rule of parts #7: If you must replace the same soldered-in component more than once, think about installing a socket, next time.
Stortz's rule of parts #8: If an EXACT part is not available, do you have something close in value? If so, but you are not sure how it will affect the performance, call the tek-support people. "Hey, your model xxxx normally has a 9.2V zener diode for component ZD-3. Ours is shorted and we are off the air. However, I found an 8.4V zener on my shelf. Do you think I might be able to use this until you can send me the correct part, if I reduce power a bit?"
Stortz's rule of parts #9: If no part is available and you are off the air, try something way out: would the equipment work without the defective part? Can the failed area be bypassed? Can you think of a temporary repair? From what available material could a repair be made?
One of my first transmitter repairs was for a failed screen capacitor, that was built into the base of an IPA tube socket. It was a weekend, of course, and nobody returned my call from the manufacturer. To get back on the air, I rebuilt the capacitor with about 3 sheets of plastic, cut out of a transparent notebook cover. I had no idea what the melting-point of the plastic would be, not how hot the socket became while operating, or the effective capacitance, or voltage break-down rating, so I sandwiched in some silicone RTV for good measure. The socket held, at half-power. The next day, I went up to about 3/4 power. After the new part arrived, I moved the power back up to 91%, and eventually to 100%. We ended up running that way until the next regularly-scheduled maintenance shut-down. Then I kept that old tube socket for future emergency use [it was better than nothing and was working when removed].
Stortz's rule of parts #10: After the panic, and you are back on the air, consider if you might be able to salvage the old part. For example, many plate blockers tube sockets [also, tubes] and blowers can be rebuilt. This can provide a spare at a fraction of the cost of a new unit.
John Stortz.
March 2001
WKES and WKZM
"Moody Broadcasting for Central Florida"