Re: 454 Fireworks -- almost fixed! Low horizontal gain

Harvey White

In the horizontal amplifier, check the values of the resistors going from emitter to emitter for each stage.  Check the value of the gain adjust and x10 pots as well.  Those affect the gain, all other things being equal.


On 5/22/2021 11:25 PM, Sean Turner wrote:
Hey folks,

Quick question. I almost have "ol sparkey" fixed thanks to Walter from Sphere and the VintageTek museum. Many thanks to both for finding me the transistors I needed to fix the vertical amplifier. That is working great now!

However, there is a problem with the horizontal amplifier. The gain is too low, and the 1X gain adjustment doesn't have enough range (to express another way: markers from my 184 are too close together).

(1) all the semiconductors in the horizontal amplifier seem fine.
(2) I probed the horizontal amplifier with the signal conditions specified in the manual and found no discrepancies.

Has anyone seen this? I thinking it could be a leaky cap or something now, but just figured someone else might have seen a similar issue in these scopes.



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