| 4Z1TL | 20-APR-2011 | TL922 |
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TL922 BURNT PLATE CHOKE |
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| Last night after some
hours of operation, another "big bang" arrived to my TL922
amp. Anode mA went up to 500mA with no signal and I shut it down
immediately. From what I recall the blower kept on for 2 minutes or so as
usual. (This is a refurbished & heavily modified
TL922. Best of the Web's modifications are implemented, & it has
worked very well over the last 12 months, except for its Anode-meter
shunt resistor which I already replaced 3 times after a "bang").
The findings this time were: 1. A large (about third) burnt area sorrounding the choke's bottom section. 2. The choke didn't open, & even maintained 160 micro Henry as per the original. (This is a home made replica of Kenwood's choke, as the first original was burnt years ago at the previous owner). 3. The 1 Ohm 5W plate-current-meter shunt-resistor gave up & opened (3rd time in a year). 4. The tubes sockets appear to have been very much heated. The surface was white clean 14 months ago. My theory (obviously I guess) is that some un wanted series resonance is to blame and not heating or poor ventilation. But how to interpret these results is beyond me. Is there any hint / clue in the burnt area's location? in its size? In the fact that the choke didn't open? I would appreciate any input to [email protected] . Thanks in advance & 73 Isaac | ||
 General
view of the choke moments before dissassembly.The burnt part seems to be right across from the tune fins and at the same height. It's all around the choke not just close to the tube. | ||
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| Burnt area is homogenous around the choke. The left side here is closest to the chasis and away from the tubes (It's facing the cariable capacitor). |
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| Dust is present on all parts of the choke but the biggest concentration was here. |
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| The opposite side of the burnt area (closest to the tubes). |
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| The heated sockets. |