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Firebird F500 component question

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Mud-Duck Jr.
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Firebird F500 component question

Post by punchcard » Friday, 27 October 2017, 19:44 PM

just finished replacing all the electrolytics in this amplifier. I am the second owner of this amp and had it since the late 70s. it is the version with the hi-lo switch. amp works perfectly now but want to add to the rebuild notes I have written down

all but one of the caps replaced were the same or close to the values specified in the schematic on cbtricks but I have a question on one of the caps in the keying circuit daughter board

the schematic shows a 100 uf 15V electrolytic for C6 which ties one side of the relay to ground. mine had a 470 uf 16V electrolytic instead

I suspect this value is fine considering it's purpose but does anyone who owns one recall what is in theirs?

TIA!


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Re: Firebird F500 component question

Post by MDYoungblood » Saturday, 28 October 2017, 12:06 PM

The cap normally found on the relay is used to delay the relay from opening (called chatter) when in SSB mode, (in AM mode the carrier keeps it closed), the higher value just holds it closed a split second longer. If you think is is staying closed too long you can change it to a 220uf, any voltage higher than 16v.

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Re: Firebird F500 component question

Post by punchcard » Saturday, 28 October 2017, 16:35 PM

MDYoungblood wrote:
Saturday, 28 October 2017, 12:06 PM
The cap normally found on the relay is used to delay the relay from opening (called chatter) when in SSB mode, (in AM mode the carrier keeps it closed), the higher value just holds it closed a split second longer. If you think is is staying closed too long you can change it to a 220uf, any voltage higher than 16v.

3's

Greg
thanks for the reply. I believe that is C4 and it was dead. that is why I re-capped the amp. well.. that and it being 40 some years old. since it has always worked fine with the 470 uf in it I was mostly just curious and trying to undo any of the wrongs the first owner may have done to it

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Re: Firebird F500 component question

Post by MDYoungblood » Saturday, 28 October 2017, 17:24 PM

C-4 is a 100uf cap going to the standby switch from the transistor (Q1) to keep it from arcing, C-6 is connected to the SSB tabs of that switch. If you are just switching out the old caps for new keep the same values and there shouldn't be a problem.

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