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previous: SpeedRacer Best bet is to go to the Triode Ele... -- 11/30/1999 4:54 AM

Re: 7189 ratings/bias point

12/1/1999 1:26 AM
SteveR	Re: 7189 ratings/bias point Thanks Speed. I'm not clear on something though. You say, "If you have a tranny picked out (so you know your load) just plot it (1/imp is slope) and adjust the idle point..." I'm using a 5k Hammond SE transformer. I'm not sure of the "it" I'm plotting and I don't know what it means that "1/imp is slope". Sorry if I seem dense about this. If I understand correctly I basically determine the bias current by finding on a load line chart where the plate voltage intersects with the dissipation curve. Then I should set the bias to something close to but not exceeding this current value. Is this more or less correct? I couldn't find any graphs that indicated load had anything to do with bias. I could only find info about 6bq5s at Ned's sight, but I found a little 7189 info from Duncan's data sheet locater. There were only specs though, no load lines, and they were virtually identical to 6bq5 specs. I think I'll use the 6bq5 specs as a guide. Perhpas I'll be a bit liberal, exceeding 6bq5 specs, but then should be pretty conservative for 7189s. Thanks for the caveat about pinouts. It appears that the 6bq5 and 7189 are the same where the 7189A has pins 1&2 and 6&9 jumped internally. I'm not using any of these as solder terminals, so I think I'm OK. thanks again, SteveR

12/1/1999 1:26 AM

SteveR

Re: 7189 ratings/bias point

Thanks Speed.

I'm not clear on something though. You say, "If you have a tranny picked out (so you know your load) just plot it (1/imp is slope) and adjust the idle point..."

I'm using a 5k Hammond SE transformer. I'm not sure of the "it" I'm plotting and I don't know what it means that "1/imp is slope". Sorry if I seem dense about this.

If I understand correctly I basically determine the bias current by finding on a load line chart where the plate voltage intersects with the dissipation curve. Then I should set the bias to something close to but not exceeding this current value. Is this more or less correct? I couldn't find any graphs that indicated load had anything to do with bias.

I could only find info about 6bq5s at Ned's sight, but I found a little 7189 info from Duncan's data sheet locater. There were only specs though, no load lines, and they were virtually identical to 6bq5 specs.

I think I'll use the 6bq5 specs as a guide. Perhpas I'll be a bit liberal, exceeding 6bq5 specs, but then should be pretty conservative for 7189s.

Thanks for the caveat about pinouts. It appears that the 6bq5 and 7189 are the same where the 7189A has pins 1&2 and 6&9 jumped internally. I'm not using any of these as solder terminals, so I think I'm OK.

thanks again,

SteveR

Replies:

SpeedRacer oops.. it was the 7189A I was think... -- 12/1/1999 2:16 AM