[Amps] TL922 Filament Transformer (Was TL922 Fan)

[Jim]

Because you say you want to ground the grids and do other updates.
*This is what you said:*

/*_Tomorrow I will detail the rest of the TL-922A makeover, new tube 
sockets, new band switch, new tubes and a W8JI grid grounding party_*

/Which means to me, that you are going to do other work? So what does 
this mean to you?


What I said is exactly what I mean. If a tube shorts, (filament to grid 
which is the only way I have seen a 3-500 tube short, and they do it 
often), it shorts the 120 volt DC bias and relay supply to ground, and 
burns up the filament transformer, because it has no fuse (fuse wont 
protest it anyway, putting a fuse in the primary does not keep it from 
burning up). Every wonder why so many TL-922 filament transformers go 
bad? This is why they do.

Only fix is to re-wire the relay bias switching.


*Bottom line...*
if you wire it like this, (from an SB220 schemaic) it will save your 
filament transformer.


//

Thanks
73
Jim W7RY

On 5/8/2019 1:28 PM, Artek Manuals wrote:
> Jim
>
> A perhaps important point but I am not sure what it has to do with the 
> fan replacement?
>
> Maybe you would just like to point us at a solution to the mentioned 
> problem rather than have us reinvent the wheel
>
> ?????????????????????
>
> Dave
> NR1DX
>
> On 5/5/2019 9:29 PM, Jim wrote:
>> You have not mentioned the most important part...
>>
>> Re-wiring the 120 volt cut off bias.� If a tube shorts, it takes out 
>> the filament transformer.
>>
>> Study the schematic.
>>
>> Thanks
>> 73
>> Jim W7RY
>>
>> On 4/29/2019 7:52 PM, Artek Manuals wrote:
>>> OK after a bit of sleuthing and help from the A/C repair guy next 
>>> door who has a meter that measured the airflow I found two probable 
>>> exact replacements for the fan in the TL-922A... Which suggested 
>>> that this was an ~53CFM fan that originally was spec'd at 100V/7W 
>>> probably 1700RPM. Size: 120mm x 120mm x 38mm
>>>
>>> The first from Mouser is a Sanyo Denki fan #109S006 a very quiet fan 
>>> at 28dBa. Problem is that it is a non stocked item with a minimum 
>>> order quantity 40pcs at $24.76 ( extended order price of $990 !) ... 
>>> deal breaker for sure
>>>
>>> With the spec sheet for the Sanyo in hand I could now look for other 
>>> equivalents ! . I found the following on Amazon.
>>> "AC Infinity LS1238",� 62 CFM @32dba� 120V/8W (probably 7W at 100V). 
>>> $14.99 free overnight delivery ...Bingo
>>>
>>> Easy replacement. The new fan though rated at 62CFM measured closer 
>>> to 55CFM installed in the amp. The old fan would raise the noise 
>>> level at the operating position when switched on by approximately 
>>> 12dba as measured with two different phone apps. The new fan 
>>> switched on raised the noise level by only 2db when switched on a 
>>> big improvement over the old worn out one. Air exit temperature was 
>>> identical to the old fan at around 30C at idle and 35C key down for 
>>> 2 minutes.
>>>
>>> So TL-922 owners� print this info out and store it with your manual
>>>
>>> Tomorrow I will detail the rest of the TL-922A makeover, new tube 
>>> sockets, new band switch, new tubes and a W8JI grid grounding party
>>>
>>>
>>> Cheers
>>> Dave
>>> NR1DX
>>>
>>>
>>>
>>>
>>>
>>>
>>
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