smurfer77
Super Member
Simply beautiful! Here's hoping it sounds as good as it looks!
I can already answer that one; the sound fantastic. Maybe best I own but I am holding off making that claim until I listen a little longer. We may dethrone the 777A with this set...
Back to the rebuild, one of the most obvious things on both HF-V60 is a pair of cooked looking resistors.
And here is the pair from the other HFV60:
I peeled off the plastic cover and found it is only the cover that is brown. Nevertheless it is suspicious; in one amp they measured 50kOhm (as they should) and in the other amp both had gone high value to ~80kOhm. So I replaced both pairs while I was at it with 2W metal film resistors (originals were 1W).
But of course, one has to ask why did they get cooked? Well those resistors are plate loads on the 6SN7 phase splitter dropping the 290V feed from the power supply to about 115V. I've seen it several times...what happens is that a coupling cap between the previous stage and this goes leaky, the current feeds into the grid of this stage and lifts the grid voltage closer to the cathode, effectively biasing the tube more 'on', resulting in plate current and this current heats up those plate resistors. When this happens you will sometimes see the plate voltage is low as it gets pulled down as more voltage drops over those cooking plate resistors that are taking extra current with the tube being switched 'on' more. Long story short, the coupling caps between the first 6SN7 and the second, have to be replaced. however, I have experienced with the coupling caps in these units and know from experience I need to replace all of them (sometimes it makes sense to replace only the last set of coupling caps, to product the OPT).
So all coupling caps are going. The large axial electrolytics will also get replaced as they are easy to access. I did measure them are they were okay. All power supply caps measured ok in terms. I have decided to leave the multi-section caps for now - I've never seen a bad one from the Sansui tube era (with tube gear they made them robust enough not only to withstand operation but rather catstrophic faults elsewhere). All PS caps measured great in terms of both C and ESR. Leakage seems to be ok too, but i will not call that definite for now.
Here you can see new coupling caps, axial electrolytics and those new phase splitter resistors (note that those should be reasonably well matched...). Multisection caps and those brown rectangular (mica) caps are left alone for now. All other resistors were checked but looked okay. I will revisit the topic of those brown rectangular mica caps later (people generally leave them... but I'm having some bad experiences....)
So here is what came out so far - I will keep all parts, so that this could be restored to original form if desired.
At this stage, with coupling caps replaced, I have fired them up in full fury for the first time. You can drive them from a modern high output line level source directly if you want (0.62V in will get you to 10W out according to the spec sheet and that makes sense with what I see in my notes that I have 11.7W with 0.7V in). I'm not going to go into the sound quality for now, as you will learn I'm actually not done with these yet. But lets just say it didn't disappoint! And then when I drove with a preamp (BA-F1) things only got better.
FYI: I used Cornel Dubilier polypro coupling caps ranging in voltages from 1kV to 2kV rating. I've used them before and I like both the specs for the job, as well as the understated white colouring - to me it looks more the part than some shiny gold parts.The axial electrolytics I struggled on a bit more as the options for 500V range in the right size are limited - in the end I found some with great temp and ripple specs etc. If I recall they are sprague. I 100% know that the original parts were overspec in terms of everything except C, and I tried to keep to this philosophy, strictly.
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