Park 75?

Schematics, layouts & other technical mumbo jumbo.

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PlumCrazy
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Park 75?

Post by PlumCrazy »

May not be the best place to ask, but you guys have surprised me before. Looking for a schematic for a Park 75. I have a Traynor YBA-1A chassis on the way (chassis, iron, pots, knobs - but no board). I don't know if I want to build a YBA-1A - I might take it in another way. Thinking a Park 75 or maybe a 50W Hiwatt.
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Dr Tony Balls
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Re: Park 75?

Post by Dr Tony Balls »

PlumCrazy wrote:May not be the best place to ask, but you guys have surprised me before. Looking for a schematic for a Park 75. I have a Traynor YBA-1A chassis on the way (chassis, iron, pots, knobs - but no board). I don't know if I want to build a YBA-1A - I might take it in another way. Thinking a Park 75 or maybe a 50W Hiwatt.
I dont know that a published schematic for a Park 75 exists but its pretty easy to glean whats going on (and its similar topographically to a YBA-1). The big takeaways IMO are 1) shared cathode on V1, 2) no bypass cap on V2, 3) no bright cap, and 4) ~500pF mix cap, 5) solid state rectifier. This puts is squarely in Marshall 1986/1992 (bass/super bass) world, so thats your base schematic to reference.

The YBA-1 is quite similar but has a bright cap and no mix cap. Small changes and easy tinkering. The other thing is that is seems most Park 75s were running KT-88s while YBA-1s ran 6CA7s. Its doubtful to me that the YBA-1 chassis holes will be far enough apart to run KT88s, but maybe you can switch it up and run KT-77s or something to get that KT sound.

50W Hiwatt is a different beast all together. Also needs room for one extra tube and one extra control pot on the front so you'd be doing some shoe horning. If you wanna bridge the gap and get a lil more clean out of plexi circuit try popping a 12AT7 in the phase inverter spot.
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PlumCrazy
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Re: Park 75?

Post by PlumCrazy »

Thanks. I'll have to see what I have when it gets here. I'd rather not use NOS tubes which is why the high potential screen voltage scares me with the Mark 2. I was thinking of taking advantage of the higher voltage to get an amp with KT88s since it's about the only thing I don't have in the collection. I'm not really keen on punching holes and usually just get vintage amps back in shape before I play them - I make the exception for mods if the thing has been thoroughly effed-with.
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