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In Reply to: Re: 845 Monoblocks help required!! posted by Sherlock on March 30, 2006 at 07:24:10:
HiAll sorted..2 blown fuses (wonder why?!), changed and replaced.
The distributor was A1 and was screaming over the phone at (allegedly) the boss of Ming Da, since this was the 2nd time I've had problems with them. He even sent through pics he had taken to show step by step how to change the fuse. Kudos indeed.
Panic over for now...
Thanks for your interest and help Sherlock, much appreciated.
Follow Ups:
Good deal.....sounded like a fuse issue. Wonder how they blew? Dont forget to check your bias (if necessary)
One posibility is the high inrush current. Its enough to dim the lights on turn on. I bought a pair of these amps years ago to re-develop. One of the first things I did was to build a delay circuit into them. A cheap and simple way of limiting the current is to install some Inrush current limiting devices in series with the power switch. Various types and values, eg cold resistance about 40R ... hot (normal running) a fraction of one R.
Hi NazInteresting info again thanks... Is this the kind of delay circuit you are referring to?
http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=5869841754&ssPageName=MERC_VI_ReBay_Pr4_PcY_BIN_Stores_IT
This delay circuit is primarily built to delay HT to the tubes to allow warm-up and avoid cathode stripping. The sort of problem I'm referring to is caused by the high instantaneous current that you get charging the HT caps and to some extent, supplying initial voltage to cold heaters. A choke can help the HT problem as a by-product of providing other very worthwhile benefits. The link will explain a little more.Naz
- http://db.audioasylum.com/cgi/m.mpl?forum=tubediy&n=92325&highlight=inrush&r=&session= (Open in New Window)
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