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This circuit is wired correctly for 115v...
You're correct in assuming the fuses blow without any load; however they didn't start blowing until I tried to apply a load.
After removing R1 and R11 you say to check and make sure the transformer is working. Would I do that by measuring output voltages (those are the only voltages I see to check for on the schematic?)
As soon as the rest of the curcuit will be separated you can use a DMM to check if the C3, C6 or D4, D6 is working (positive probe - to positive of C3, negative probe - to the negative of C3, resistance should be very high. Then the same thing you should do with C6).If all is OK after the last step - you should try to replace (one at a time) U1 and U2.
Hi Poty. Here's what I've done so far in order:-Installed 250mA slow blow fuse (closest to 63mA I could find locally.) I measured close to 0VDC on the 15V outputs.
-Removed R1 and R11 and measured 24.9V AC in their places. Fuse is good.-Installed R1 and R11. Removed R2 and R12 and measured 33.5V DC in their places. Fuse is good.-Installed R2 and R12. Removed U1 and U2. I then measured 33.43V DC across C2 and C5. Fuse is good.
So I'll be measuring resistance across C3 and C4 (capacitors) and then measuring resistance across D4 and D6 (diodes) and then C6 (capacitor?) I only need to test those two diodes?
When I replace U1 and U2 where do I measure to see if they are working ok? Also, when you say to install them one at a time would that mean Install U1 take a measurement then remove U1. Install U2, take a measurement then remove U2. Or does it mean install U1 and take a measurement and then install U2 and take a measurement?
Have you tried to power on full device with the fuse?Slightly excessive voltages, but it seems all is rather in margins...Replace U1, measure the result on the first output (TP1-TP5). If all work OK - put U2 (the U1 stays in place). Measure the result on the second output (TP10-TP7).
With U1 in place I measure 14.98V on TP1 and TP5. With U2 in place I measured 14.92V on TP10 and TP7. No fuses have blown so far. I guess that means it works now!
Because every resistor, capacitor and diode measured as it should have, did removing U1 and U2 maybe "reset" something in circuit?
I'm completely perplexed by this whole situation and frankly, I'm scared of installing the brand new blue LED I bought for this circuit. Should I keep the 250mA slow blow fuse in there?
With full load on 115V the device should draw near 40mA. At the start time it may be 2-4 times more. It is possible that "slowness" of the fuses was not enough to sustain the inrush current.
I checked my AC voltage at the transformer inputs and it measured at 121V. I can't do the math but maybe it was drawing too much.
It seems that I have the exact same problem (almost verbatim) as this fellow: http://www.audiocircle.com/index.php?topic=88485.0I'm using the 18v transformer and also using replacement regulators (per jim's replacement sheet.) However, that topic died off with no resolve so I'm wondering if there's an issue with the value of R4 and R7 and the 18v transformer?
R4 and R7 are 1k. I measured 23.5vAC across each resistor. That means that I have 0.0235 amps and 0.55225 watts across each resistor.
Hi, poty. I just double checked my DigiKey order and all the resistors I ordered are all metal oxide rated at 1W.
... the fine print in the data sheet .. says not to brush the resistors when cleaning as it may damage the coating. I definitely brushed them with alcohol during the cleaning process.
datasheet ... ERG1SJ102...
I'm also reading 29 volts across the large caps which are rated for 25v.
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