[jshorva65]

Here's the current staus on my client's RCA 621TS that needed the new 7DP4 thanks to FedEx. It's almost completed, but there are still some issues to be resolved.

There's a known issue with RCA's KRK-2B 13-Channel tuners involving some solder joints deep inside the unit which I've got strong suspicions of being the root cause of a tricky Intermittent on this 621TS. When first powered up, it takes almost five minutes after the raster appears for the set to produce picture and sound. Since the change in performance manifests as a sudden "popping in" effect and the cycle only starts over if the set is powered down and subsequently powered again from a "cold start" as opposed to being briefly shut down for a "warm" restart, and the bias and B+ voltages remain within specifications both during and after the symptom period, these indications point to a solder joint inside the tuner itself. The prime suspects are the jumpers which join the wiper contacts for each of the pairs of wafer switches (RF/Mixer/Oscillator) and seems more likely to be the jumper in either Mixer or RF since very weak video is evident (out of sync due to simultaneously insufficient sync amplitude) while the symptom is occuring, thus suggesting that the Oscillator must indeed be running and somewhat near its correct frequency.

It's a shame that Louis Stangle of Quality Tuner Service no longer services 24 MHz IF tuners. He did a fantastic job with the 44 MHz Oak TT-166 wafer switch tuner from my Philco 16M91 and at a very reasonable price. We're sufficiently comfortable with servicing drum-type tuners of the 24 MHz IF variety, but have yet to acquire enough practice with "expendable" examples of wafer switch tuners of either IF band to achieve the necessary level of mastery for us to attempt the kind of delicate surgery that Hugo Holden performed on the tuner in his 621TS. Instead, we still prefer to send such work to expert Tuner Surgeons such as Louis.

At any rate, here's a pic of what we've got so far with Jeff's 621TS. We're definitely on the right track, but we still have a ways to go. Many thanks to Todd for the great Restoration work with the finish. Thanks also to Big Dave for the double-checking of everything where my being considerably nearsighted might have caused me to miss some tiny detail had I relied on my eyes alone.