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From: gap5444@lims03.lerc.nasa.gov (Greg Priddy)
Newsgroups: rec.audio.high-end
Subject: Re: Miscellaneous Comments
Message-ID: <9944@uwm.edu>
Date: 5 Mar 91 13:59:11 GMT
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In article <9903@uwm.edu>, Daniel_Rai@ub.cc.umich.edu writes...
> 
>     A Dyna Stereo 70 keeps blowing the main fuse
>     seconds after powering up.  The tubes are fine,
>     and they all light up before the fuse blows.  What
>     could be causing this?  Is there troubleshooting
>     in the manual? (I've heard of a place in Ohio that
>     sells Dyna parts - I don't have a manual, but
>     think I can get one from them)  If it is the input
>     board, I'm thinking about replacing it with one of
>     those solid state boards from Sutherland
>     Engineering, or from a few other companies.  Has
>     anyone tried these things?
> 
As a long-time owner (and subsequent fixer) of a Dyna Stereo 70, I can say 
with some certainty that it is not your input board which is causing the 
blown fuses.  If you are sure that your power rectifier tube (5AR4) is good 
then you probably have either a bad filter cap or bad bias cap(s).  In any 
event, it is likely that something in the power supply section is awry.

Stereo Cost Cutters of Dublin, OH does sell Dyna parts (including whole 
"new" amps), as does Audio by Van Alstine of Burnsville, MN.  About all I 
have seen in the way of a manual is a schematic and parts list.  There is 
also a place in Lakewood, OH (near Cleveland) called Play It Again Sam, which 
does excellent work on all sorts of stereo equipment, including Dyna's.

As far as solid state input boards and other mods, there are as many 
opinions as there are experts.  IMHO, unless you are dissatisfied with the 
way the amp sounds, I would try to stick to the original circuit topology.  
Replacing the old resistors and caps (which have probably drifted out of 
value) with new precision parts would be my recommendation.

I have no affiliation with any of the places mention herein, and my 
opinions, for better or worse, are based on my experience and do not 
represent those of my employer or my employer's clients.

Good Luck!

-Greg