Supro 1616T

vintage soul

"This old amp, it's got stories to tell. Gritty, funky, and worn. The pulsing heartbeat of the tremolo, always begging to slow down. Late-night smoke, sweat, blood, and whiskey-tinged t-shirts. Life on the verge of distortion.”

After years of soul-stirring service, my Airline 62-9029a (also known as the Supro 1616T and Gretsch G6151) suddenly developed volume fluctuations, low output, and a non-functional tremolo. Time to take it to the workbench!

Troubleshooting: Initial Checks

I swapped the tubes with known good ones, but the issues persisted. Tube tester gave all tubes a clean bill of health. I then visually inspected the amp's interior for broken joints, burned resistors, or obvious faults. Quickly performed the chopstick test to detect loose solder joints.

Classic rat nest of wires. Yikes!

The Culprit?

Electrolytic Capacitors

Original electrolytic capacitors were long overdue for replacement! Time to replace those expired capacitors and breathe new life into this vintage gem! Out went the original can capacitor; in came 2x - 10uF/450V and 1x - 22uF/450V (replacing 20uF/450V).

New capacitors are tucked in the corner of the amp on point to point posts. I give them added stability by using Permatex RTV to hold them, so they don’t move or rattle. The amp is a studio amp so it shouldn’t be taking too much of a beating.

Tremolo Circuit Repair
The voltage dropping 6.8K resistor (at 20uf/450 capacitor) was charred and broken, showing infinite resistance. Replaced with 1W metal film 6.8K resistor. Visually inspected the other resistors and capacitors in the circuit, and they all look good.

Broken resistor causing tremolo to stop working.

Back to Life!

I prioritized only the essential repairs to maintain the amp's original character and tone. Also, I really wanted to get back to the recording session! After the above repairs, the volume is consistent and loud; tremolo's working beautifully. Time to rock! <Links to music here>

Future To-Dos:

In the pre-amp, replace older 35uF/50V electrolytic cathode bypass cap (12AX7)

In this photo, the 330 ohm 2 watt cathode resistor (6v6) looks like it has taken some heat over the years. It measures 356 ohms and is working fine, but should be replaced at some point for longevity.

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