I was sick at home today with a sore throat, but was well enough to notice, and snag later on, an old Heathkit amp that showed up on Kijiji for a great price. This is the same model (TA-16) that a high school buddy of mine built, and I was so jealous of. A nicely made clean-sounding 25W solid-state amp with 2 channels, 2 x 12" cab and the classic reverb/trem of the era.
Since there is lots of room, and because I know more now than I did in high school, I was thinking of some mods. One of them was a tremolo speed indicator. Looking over the schematic, the tremolo is almost identical to that of the fabled EA tremolo. The component values are different but the circuit is essentially the same as you can see below.
On the left is the amp's circuit, and the right is the runoffgroove version of the EA trem, with a speed indicator LED.
Should I assume that I can stick an LED between the 6k8 resistor going to the collector of Q12 (R61) in the same fashion as it is inserted between the 10k resistor and collector of Q3 in the EA trem on the right? If so, I assume that a slightly larger value of resistor should be used for the LED, given the 13v supply?
(http://img.photobucket.com/albums/v474/mhammer/TA-16EA.png)
Quote from: Mark Hammer on April 01, 2011, 07:38:06 PM
Should I assume that I can stick an LED between the 6k8 resistor going to the collector of Q12 (R61) in the same fashion as it is inserted between the 10k resistor and collector of Q3 in the EA trem on the right? If so, I assume that a slightly larger value of resistor should be used for the LED, given the 13v supply?
Yes just stick the LED in series with R61. You don't need to increase the resistor, the current is not going to exceed 16mA even on peaks.
I'll do just that....once I figure out how to get the amp chassis out of the cabinet to work on. :icon_lol: