The rectifier diodes, one is 1,000PIV like a 1N4007 for the +400VDC, and the 50VDC 4-diode bridge is another 1A affair so I would put a 1-2A 200PIV part like 2KBP002M (2A 200PIV)
Given the age of the tuner, I would check for a shorted electrolytic capacitor in the power supply or motor.
It would be best to replace them all, maybe a dozen parts. I know professional piano tuners who need reliability when they are doing a job and $25 investment is worth it.
Check the two motor drive power transistors, if they have shorted it would overload the rectifiers and you will just keep blowing fuses. You can put a 40-60W light bulb in series with AC mains power to the unit while checking for shorts, it will just light up if there is an overload.
Thank you greatly, I was at a loss as to where to even begin finding specs on those diodes. Considering I have to buy the diodes and replace them anyways, it really makes sense to go ahead and do the caps. I use it to set up and tune various stringed instruments, and I too can appreciate the small investment into reliability.
Some notes on what I did to mine and some views of what was in there: http://medpants.com/strobe-tuner-refurb
I came across your write up when trying to find some more technical data, it's kind of funny to see how many little changes they made to the model. Mine is almost identical to yours, except the power cord and mic input are on a little cut out on the side and the power cord is detachable. I imagine it would take quite some experience to date the individual revisions. I wasn't crazy about the Astatic mic that comes with them usually, but I couldn't bring myself to drill into the face plate. Mine is fairly stationary, and it's actually nice to be able to run the mic closer to the sound source of whatever you may be tuning. One thing I may do in the future, particularly if I can find a spare face plate or second tuner, is add a line input for tuning in louder environments.
That's an interesting contraption, I've never seen one before, how does it work?
The above advice looks like it pretty well has you covered, the diodes are not critical and lots of different types can be substituted but it is possible something downstream has shorted and caused the diodes to fail.
They really are neat little devices, and so precise. Peterson is pretty much one of only two names in the precision tuner game, with a long standing history. I don't know that the strobe device is necessarily still the best display for it, digital readouts giving you fractions of cents is probably more concise, but there is just something warm and comforting of the neon indicators and that disk whirling around. Changing from note to not isn't as easy as your standard chromatic tuner, but come on, this thing is worth it.