Gary, that's a really nice looking switching regulator circuit. As far as I know, the board doesn't take more than 1Amp, but as Fabio pointed out, the 7805 I'm using is capable of upto 1.5A, which I did not know, nor planned. I will take a current measurment of my system when I can. I'm curious about other S-100 systems, do you use exactly 8V? Since mine is putting out 8.9V, I wonder how much difference it would make at 8V.
Cheers, Josh Date: Sun, 20 Jul 2014 08:29:48 +0200 Subject: Re: [N8VEM-S100:4642] 8080 CPU - Heat is ON - Wet Finger Test From: [email protected] To: [email protected] Gary, Yours is a very good idea (and I bought a few of those regs for my own use) but I fear there is a chance we cannot use them on this board: Josh mentioned using an 1A v.reg on the board, but from the photo he posted on a previous thread about the 8080A card I see he used an L7805CV, which does 1.5A. I wonder if the filled card goes above the 1A barrier... If not the switching regulator can really be the definitive (and backward compatible with IMSAI cabinet) solution to the problem. Fabio On Saturday, July 19, 2014, Gary Kaufman <[email protected]> wrote: Josh - There's a tiny 1A switch mode voltage regulator on Ebay (Item 261355553215) and directly on the seller's site: http://www.elabpeers.com/40v-to-5v-voltage-regulator-lm7805.html Looks like it might be a perfect fix for the problem here. I suspect the problem isn't the 1A rating, but rather the thermal limitations of the TO-220. I've ordered two and can report back once I receive them. I offered the seller $9.50 each / quantity 2 with the ebay "Make an offer" and it was quickly accepted. - Gary On 7/19/2014 11:49 AM, John Monahan wrote: Just want to mention, people may want to consider using the 1.5A To-220 regulators rather than the old 1A 7805's. For example a L7805CV (Jameco #924633). Indeed I seem to remember Mouser had 3A 5V's in a TO-220 package. There are a lot of chips for one 7805 on that board. On a V2 version Josh, you might want to consider a 3A LM232K, I know they are a real pain to get, take up much more room, but they do run much cooler. Alternatively put two To-220's on the board. It's probably just me, but I don't like hot boards. Over time the fiberglass starts to deform/change color... minimally put a mica washer between the heat sink and board. Also use heat sink paste. John From: [email protected] [mailto:[email protected]] On Behalf Of Crusty OMO Sent: Saturday, July 19, 2014 5:34 AM To: [email protected] Subject: RE: [N8VEM-S100:4637] 8080 CPU - Heat is ON - Wet Finger Test Hi Guys, Because the 7805 can get hot, I want to just issue a safety warning for everyone. Hopefully, most of you already know this, but just in case, it's always a good idea to remind and inform the new comers. When powering a board for the first time, be ready to check the voltages and monitor the heat of the regulator(s). Cut power off at the sign of any trouble. When monitoring the heat of the regulator by finger, always use a wet finger. Doesn't sound right near electricity, but hopefully you have a properly grounded power supply and chassis. The wet finger will prevent severe burns if the temperature is over 100c. When it's over 100c, a quick light tap on the surface with a wet finger will give a quick sizzle. It's like testing the temperature on your clothes iron. The best way is to use an infrared surface thermometer, but I only got one of those a few months ago. Up to now, I've always used the wet finger without incident. Regards, Josh Bensadon -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.-- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout. -- Dott. Fabio BattagliaBlog - http://mercatopo.blogspot.com -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
