Lindell No. 603

[52 Bill]

Earlier on you posted that the input transistors were 2SB54's. Can you use one of those for the driver position and replace the input with another less critical one?

[patlaw]

Earlier on you posted that the input transistors were 2SB54's. Can you use one of those for the driver position and replace the input with another less critical one?

I ordered a couple of generic replacements on eBay. We'll see if they work. If not, there are some actual ones here. The one that's making noise is very noisy when it's hot. I do hope it's the transistor and not a leaky capacitor, which I've checked.

[patlaw]

Just to close the loop on this amp, I've done all I'm going to do to it. I replaced the .47 uF caps in the tremolo section, and the tremolo works, although it is faster than I would have thought it should be. The resistor and pot values in tremolo circuit are right, so I'm going to leave it. It could have been that way from the factory.

All electrolytics were replaced.

The 2SB54 driving the phase-inverter transformer was leaky. An NTE102A that I got from eBay worked fine. No more hiss or declining-with-time audio performance.

There's no way for me to know whether the amp sounds like it should. There's a good chance the speaker is bad. I substituted my Sunn Sentura II cabinet for the speaker, and it still didn't sound great, but considering this amp is a design from a record player or car radio, I'm not surprised.

If I were to do any more work, I'd probably hand select caps for the tremolo circuit, replace the four remaining germanium transistors, and replace the speaker, all of which is just silly for the piece-of-crap amp.

It was an interesting project. I never did find a schematic.

[vintagekiki]

It was an interesting project. I never did find a schematic.

Put the amp in front of you, take the pencil and paper in hand, and for an hour or two draw schematics, and surprise the forum by uploading the schematics.
Not complicated, it's only 5 transistors and several resistances and a capacitors.

[galaxiex]

Just to close the loop on this amp, I've done all I'm going to do to it. I replaced the .47 uF caps in the tremolo section, and the tremolo works, although it is faster than I would have thought it should be. The resistor and pot values in tremolo circuit are right, so I'm going to leave it. It could have been that way from the factory.

All electrolytics were replaced.

The 2SB54 driving the phase-inverter transformer was leaky. An NTE102A that I got from eBay worked fine. No more hiss or declining-with-time audio performance.

There's no way for me to know whether the amp sounds like it should. There's a good chance the speaker is bad. I substituted my Sunn Sentura II cabinet for the speaker, and it still didn't sound great, but considering this amp is a design from a record player or car radio, I'm not surprised.

If I were to do any more work, I'd probably hand select caps for the tremolo circuit, replace the four remaining germanium transistors, and replace the speaker, all of which is just silly for the piece-of-crap amp.

It was an interesting project. I never did find a schematic.

And likely never will unless you draw it yourself...

I have tinkered with quite a few of these cheap transistor Japanese made amps (Teisco, Audition, Kingston, etc) from the 60's 70's.

On every one, the tremolo has been quite fast even with new stock value caps and resistors checked for spec.

On some I have had to make quite drastic changes to the circuit values to get the tremolo to have a nice range from "normal slow" to moderately fast.

Not sure if you are still interested, but...
I have quite a few postings over on the SSGuitarAmp forum where I traced circuits and drew schematics for them.
(have to join and log in to see the pics/schematics)

https://www.ssguitar.com/index.php

I guessing you are done with this amp tho...


...and to add to what vintage kiki said...
I found it quite fun and a nice challenge to trace the circuits and make schems for them.... but I'm weird that way....