Dutchboy Posted July 13, 2020 Share Posted July 13, 2020 I picked up a push button style PEB that was not working. The fan powered up but nothing else. I figured it was the fuse and/or the transformer. The external fuse is good I checked it. Does that push button style PEB still have a fuse in the transformer? Or do I need to replace the whole transformer? The whole PEB is apart but I don't want to cut into the transformer if it doesn't have a fuse in it. Quote Link to comment Share on other sites More sharing options...
tuf Posted July 13, 2020 Share Posted July 13, 2020 Did you test the voltage coming out of the supply? Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted July 13, 2020 Share Posted July 13, 2020 44 minutes ago, Dutchboy said: I picked up a push button style PEB that was not working. The fan powered up but nothing else. I figured it was the fuse and/or the transformer. The external fuse is good I checked it. Does that push button style PEB still have a fuse in the transformer? Or do I need to replace the whole transformer? The whole PEB is apart but I don't want to cut into the transformer if it doesn't have a fuse in it. The pushbutton type with the fuse holder on the back should not have a fuse in the transformer. Do you have a DMM? 1 Quote Link to comment Share on other sites More sharing options...
HOME AUTOMATION Posted July 13, 2020 Share Posted July 13, 2020 1 hour ago, Dutchboy said: cut into ...Literally??? 1 2 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted July 13, 2020 Share Posted July 13, 2020 Actually, I think ALL of the PEB transformers have a small fuse buried in them. It is usually the first thing to go if a card shorts something on the bus. . .there is a document out there showing where to dig to find it--and how to safely replace it. 1 Quote Link to comment Share on other sites More sharing options...
fimbulvetr Posted July 13, 2020 Share Posted July 13, 2020 Well, the symptoms sure sound like a transformer fuse. No idea if all of the PEBs have them or not though. http://www.mainbyte.com/ti99/peb_pow/peb_pow.html Quote Link to comment Share on other sites More sharing options...
fimbulvetr Posted July 13, 2020 Share Posted July 13, 2020 Interesting: "Additionally someone also asked Lee why they decided to put a fuse for the PEB power supply inside the transformer? Lee said "it was a dumb idea" but also added that it kept the consumers from putting a fuse that was not rated for the system in the unit thus bypassing the safety that the fuse they had in it." http://www.texndixie.com/lubbock.htm Quote Link to comment Share on other sites More sharing options...
atrax27407 Posted July 13, 2020 Share Posted July 13, 2020 I think that I would be more comfortable with Ksarul's analysis than the one offered by TI-Omega. 1 Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted July 13, 2020 Share Posted July 13, 2020 1 hour ago, atrax27407 said: I think that I would be more comfortable with Ksarul's analysis than the one offered by TI-Omega. I never heard that the original P-Box (the one with the fuse holder on the back) had a fuse in the transformer as well. I guess you learn something new every day. I was told, by a source that I thought reliable that TI made the switch to save pennies later on the rocker switch type P-Boxes. I figured if he had a DMM he could at least test to see if any current was making it out of the transformer, if not it would at least isolate the issue to that point. Thanks for setting me straight. LINK ONE LINK TWO From Mainbyte... Quote Link to comment Share on other sites More sharing options...
fimbulvetr Posted July 13, 2020 Share Posted July 13, 2020 1 hour ago, Omega-TI said: I never heard that the original P-Box (the one with the fuse holder on the back) had a fuse in the transformer as well. I thought the same thing, which is why I picked an older style one when I got mine. Of course, TI being TI, I wouldn't be surprised if there was a random assortment of transformers in boxes from around the changeover between the old one and the new one. 1 Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted July 13, 2020 Share Posted July 13, 2020 1 hour ago, fimbulvetr said: I thought the same thing, which is why I picked an older style one when I got mine. Of course, TI being TI, I wouldn't be surprised if there was a random assortment of transformers in boxes from around the changeover between the old one and the new one. You know, that very well could be! Quote Link to comment Share on other sites More sharing options...
Dutchboy Posted July 13, 2020 Author Share Posted July 13, 2020 Thanks for the advice. I have a DMM and will check the voltages. My guess was that TI used the same transformer and it has a fuse in it. I need the schematic for the PEB. It does look relatively straight forward. Quote Link to comment Share on other sites More sharing options...
Ed in SoDak Posted July 18, 2020 Share Posted July 18, 2020 The pdf is 35 pages, a good collection of TI schematics and info. The PEB power supply is a clip of page 11. Not sure where I got it from to just post the link, so here it is. A little redundancy never hurts! TI Circuit Diagrams and Schematics.pdf 2 1 Quote Link to comment Share on other sites More sharing options...
Dutchboy Posted July 18, 2020 Author Share Posted July 18, 2020 Thanks. I found a simpler schematic of the push button PEB online and used that but this one is better in some respects. First Omega was right only one fuse in the PEB either externally in the push button or internally. Second, when I looked at the old schematic of the PEB it looked like the fan would not run if the fuse blows on the push button version of the PEB. That is indeed the case as current goes through the fuse prior to the fan in the old version of the PEB. This is opposite of the newer one. So next I checked transformer resistance and AC voltage going into the board and DC voltage going out of the disk drive connector. I got no values for any of these. This leads me to believe the transformer is not working rather than the two voltage rectifiers. I guess I have several options at this point. 1. Obtain a working PEB transformer and install it. 2. Obtain another transformer or power source that would work with the PEB. 3. Obtain another PEB and use this one for parts. 4. Part out the PEB on Ebay. Any ideas about obtaining another transformer or alternate one/power source? I have no idea the winding ratio or how I would get 5 wires off a new transformer. Any ideas would be appreciated. Jason Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted July 19, 2020 Share Posted July 19, 2020 That was what I was trying to tell you from the beginning, as your current symptom matches a known fuse problem--your PEB really does have a fuse physically buried in the transformer windings. You can replace the external fuse all you want, but the only thing that works at that point is the fan. Here is a link to the repair instructions. Go all the way down to the bottom of the page and you will find the location of this second fuse. . .and as long as none of the transformer wiring is damaged, it will fix your problem. I have blown one or two of these hidden fuses in PEBs I own over the years--it is a pain to fix, but it really is just a hidden fuse that has to be chipped out and replaced. It would probably make sense to put the replacement in an appropriate fuse holder, but these fuses only blow when something egregious happens on one of the output voltage lines (like a dead short), so it is not a regular thing. Here are the 3A Fast Blow fuses you will need. Quote Link to comment Share on other sites More sharing options...
jrhodes Posted July 19, 2020 Share Posted July 19, 2020 6 hours ago, Ksarul said: ... hidden fuses ... If you think these are fun to find/fix, wait until you encounter a "fusable link". They're a inline fuse that pretty much looks like a normal wire. Spent a week trying to figure out a electric problem on a vehicle, only to discover it was one of these blasted things. I had never heard of them before this and i wish i never had, such a pain. Quote Link to comment Share on other sites More sharing options...
atrax27407 Posted July 19, 2020 Share Posted July 19, 2020 (edited) So, it turns out that KSARUL was correct and OMEGA was wrong. Interesting! Edited July 19, 2020 by atrax27407 2 Quote Link to comment Share on other sites More sharing options...
Dutchboy Posted July 19, 2020 Author Share Posted July 19, 2020 So I need to cut into the plastic casing of the transformer and the fuse will be inside the hard plastic? It is not on the outside under the plastic wrapping I can tell you that for sure. A lot of transformer fuses can be accessed by removing plastic wrapping not the hard plastic case. Some appliances will hide a fuse in the transformer but you can remove the plastic wrapping with a small screw driver to access it. Ok I will cut into the plastic case I guess not much to lose at this point. Quote Link to comment Share on other sites More sharing options...
atrax27407 Posted July 19, 2020 Share Posted July 19, 2020 Go to the link in KSARUL's last post and follow in the instructions. The hiden fuse was documented in MICROpendium and various other sources years ago. Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted July 19, 2020 Share Posted July 19, 2020 Again, look at the two pictures at the bottom of the page I linked to. It really is BURIED in the plastic. . .towards the bottom of the indicated side, as shown in the first of the two pictures. It is a real pain to get it open and it requires extreme care to avoid damaging things, but the fuse is in there. I attached both pictures here, as they REALLY clarify the issue. . .please read the rest of the instructions on the original link, as it will save you much grief. Quote Link to comment Share on other sites More sharing options...
Omega-TI Posted July 19, 2020 Share Posted July 19, 2020 7 hours ago, atrax27407 said: So, it turns out that KSARUL was correct and OMEGA was wrong. Interesting! Yeah, well that can happen. GIGO I guess. I think someone might want to inform whoever runs Mainbyte, because he also is apparently disseminating erroneous information as you can see from the excerpt below. Ksarul has probably forgotten more about the TI and it's history than I ever knew. 1 Quote Link to comment Share on other sites More sharing options...
atrax27407 Posted July 19, 2020 Share Posted July 19, 2020 (edited) I suggest you re-read the Mainbyte page. Pay particular attention to the third paragraph and the details of replacing the fuse. The external fuse is straightforward. The internal fuse not-so-much so. If nothing in the PEB powers up, it is likely the external fuse on the newer models. If only the fan powers up, it is the internal fuse in the transformer which is present in all models. Edited July 19, 2020 by atrax27407 Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted July 20, 2020 Share Posted July 20, 2020 Both versions of the PEB have the external fuses. The older model uses a standard screw-type fuse holder. The newer ones hide the fuse behind the voltage selection plate. If you pull the plate out to change the input voltage, you will see that there is a fuse hidden inside. Note that this fuse doesn't replace the hidden fuse in the transformer--in both cases, it is the external fuse that is expected to blow first, sparing the transformer's internal fuse. Unfortunately, that is not always the case. . .a dead short will pop that transformer fuse in a heartbeat. Quote Link to comment Share on other sites More sharing options...
yell0w_lantern Posted July 20, 2020 Share Posted July 20, 2020 Hey, guys. :) I see you've met my brother. It turns out I might be pitching in on this transformer surgery. For plastic, my go to is usually a hobby knife with a number 11 blade. Should I ready anything more robust for the patient? Quote Link to comment Share on other sites More sharing options...
+Ksarul Posted July 20, 2020 Share Posted July 20, 2020 That is probably exactly the right tool here. The plastic often breaks up if you're doing the cut correctly. Note that you also want to make sure you don't damage any of the windings in there either. This one requires a bit of careful peeling in the indicated area. . . Quote Link to comment Share on other sites More sharing options...
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