XPost: uk.d-i-y   
   From: brian1gaff@gmail.com   
      
   If you coasted your time for all this, you could have bought a new one.   
    Brian   
      
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   This newsgroup posting comes to you directly from...   
   The Sofa of Brian Gaff...   
   briang1@blueyonder.co.uk   
   Blind user, so no pictures please   
   Note this Signature is meaningless.!   
   "N_Cook"  wrote in message   
   news:ubt4ls$1caq7$1@dont-email.me...   
   > On 16/08/2023 16:59, N_Cook wrote:   
   >> 2 peltier units in one cabinet.   
   >> The lower unit lost thermostat control and on full whack continuously.   
   >> I disconected that one and run on the top unit only, but with display   
   >> panel and lower unit unpowered the top unit ran at half cock   
   >> continuously which was ok for the intended use as a non-freezer box low   
   >> power fridge.   
   >> Until , as no protection from dripping condensate , condensate drip from   
   >> the skyved heatsink physically corroded a pin of a small 78L08 100mA   
   >> volt reg., diode checking the whole board cold, main active devices   
   >> looked reasonable, fuses and low ohm Rs ok.   
   >> I had thought if that top control unit failed at any time I could swap   
   >> it for the bottom. Both are marked fanny.com.cn PCB100729K1, MP 011   
   >> Replaced the VR and no fan kick, green LED flashes on then off and red   
   >> LED on . I swapped control units and the identical green and red LED   
   >> function and no fan kick also.   
   >> No idea what to expect putting a DVM on both isolated peltier units,   
   >> top one on resistance each way was 12 ohm and -1 ohm presumably from the   
   >> dissimilar metals in series , the lower one 13ohm and -4 ohm which as   
   >> far as it goes ,are presumably ok.   
   >> Before checking out the output side of the PS active devices AZ494AP and   
   >> LM358P , conventional DIP devices, something silly I've overlooked?   
   >> I will try the lower unit in isolation tomorrow.   
   >   
   > Very humid recently and I actually saw a drip fall from the top Peltier   
   > unit while testing it , so a paxolin sloping roof fixed under the peltier   
   > and over the power supply/control board.   
   >   
   > I've decided a problem with the display board , the IC there must have 2x   
   > 7segment drivers and 2x DAC but also some sort of interconnect so you   
   > cannot have max setting on one unit and min on the other.   
   > Only wanted one unit being used for low power marginal chiller cabinet, no   
   > freezer box required,so low noise/vibration, hotel like, mini-fridge.   
   > Disconnecting that totally, the 3 wire connector marked NTC2 although no   
   > thermistor seen on that display board.   
   > Now I know both peltiers and both PS/control boards work separately.   
   > Replacing the NTC2 lead with a 22K pot across its 8V supply (instead of   
   > the DAC function of the user front panel) means low V setting gave full   
   > power 12.5V on peltier and main fans and mains consumption of 70W with   
   > both green and red LEds on, high V gave low setting of 4.7V and overall   
   > mains consumption of 12W, just red LED on.   
   > Unplugging NTC1 for thermistor inside the peltier unit and peltier+ fan   
   > drive drops from 4.7V to 3.7V and 8W consumption.   
   > AZ494 is the smps controller with error amps and dual op-amp LM358 ,  ST   
   > TO220 device is dual shottky rectifier on the LV side of the pcb.   
   > Separate isolation Tx for the fixed 8V low power supply.   
   >   
   > --   
   > Global sea level rise to 2100 from curve-fitted existing altimetry data   
   >    
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)