OTB – Tektronix 453A

I picked up a broken Tektronix 453A scope from Craigslist. It had a few issues, however none of them were fatal for this unit. I initially checked the power supply voltages and they all seemed okay. After looking around a bit more and reading the service manual I found the primary sawtooth signal was basically … Read more

OTB – Old Yellowing Plastic

I was repairing an piece of older HP test gear, and the control buttons had all Yellowed with age and sun exposure to a large degree. So I pulled them all off the system, and tried the Hydrogen Peroxide + UV treatment. This process works great!  You need 40% (or greater) hydrogen peroxide, which you can … Read more

OTB – Kenwood TR-9000

I picked up a TR-9000 from the Dayton a few years ago, It was a bit dirty and needed a little tune up. Worked for the most part, except the PLL was not locking until warmup. A detailed alignment exists for this radio and once followed all was well. It’a a nice 2M SSB radio, … Read more

OTB – HP 5216A 12.5 MHz Electronic Counter

I picked up an HP 5216A 12.5MHz Electronic Counter from a hamfest recently in Loveland CO. I figured it needed a lot of love, based on it’s condition at time of purchase.  After checking it out, found it had a totally fried resistor in the attenuator section and some very, very dirty switch contacts which … Read more

OTB – HP 3325A Sensitized Function Generator

On the Bench: HP 3325A Sensitized Function Generator. It had a completely sorted out bridge rectifier and a shorted transistor on the -15v rail. It is also had a broken power button, missing another button (Now on order) and was missing a “spring” on one of the buttons as well. Else, this tests out great … Read more

OTB – HP 5385A Frequency Counter

On the bench today is a HP 5385A frequency counter which seems to have a short to ground on the 5+ rail. Someplace….. Hunting.   Fixed: The 5v over voltage crowbar protection circuit was being switched in, because the 5V rail became noisy/ripple (+/- 700mv ripple voltage). Replaced the aged smoothing capacitor on the 5v switch … Read more

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