17-06-2021, 06:26 PM
Another happy Hedghog user. I just (finally) finished getting my Hedghog (MkI) completed and its now working very nicely, after a few hiccups.
The fine soldering was taken carefully and steadily with lots of flux from the flux pen, and the smallest solder I could find. It came out very nicely, especially after a nice clean-up with flux remover. Surprisingly, soldering in the tiny 32-pin chip using "drag soldering" (under a microscope) was virtually the easiest bit to do. The tiny resistors on the other hand had to be watched like a hawk, otherwise they tried to head for the hills (or under the bench, mostly). The tiny 6-pin analogue switch IC proved a bit fragile. Trying to remove a solder splash between pins I instead removed a pin! RS came to my rescue with relacement chips quite quickly and cheaply.
Worryingly, the kit was dead with very high current draw (>500ma) on switch on, despite the rails testing fine (about 1K across the 5V rail), but after a lot of testing, examination and desoldering, I finally desoldered the modulator chips and the fault(s) vanished. The problem turned out to be fake Chinese modulator chips, proved by seeing good composite video with the chips removed. Both chips tested identically faulty, with 200-300mA current draw each when probed outside the board with a 5v psu (+5v on pin 15, 0v on pin 16 if you need to check).
Chris Wood quickly came to my rescue with replacement modulator chips which were duly soldered in . The device finally worked after an initial heart-stopping moment with no output before we realised that the DIP switches were not yet set correctly!
So yet another huge cheer for Frank C for this lovely design. Well done, sir!
-Jeremy
The fine soldering was taken carefully and steadily with lots of flux from the flux pen, and the smallest solder I could find. It came out very nicely, especially after a nice clean-up with flux remover. Surprisingly, soldering in the tiny 32-pin chip using "drag soldering" (under a microscope) was virtually the easiest bit to do. The tiny resistors on the other hand had to be watched like a hawk, otherwise they tried to head for the hills (or under the bench, mostly). The tiny 6-pin analogue switch IC proved a bit fragile. Trying to remove a solder splash between pins I instead removed a pin! RS came to my rescue with relacement chips quite quickly and cheaply.
Worryingly, the kit was dead with very high current draw (>500ma) on switch on, despite the rails testing fine (about 1K across the 5V rail), but after a lot of testing, examination and desoldering, I finally desoldered the modulator chips and the fault(s) vanished. The problem turned out to be fake Chinese modulator chips, proved by seeing good composite video with the chips removed. Both chips tested identically faulty, with 200-300mA current draw each when probed outside the board with a 5v psu (+5v on pin 15, 0v on pin 16 if you need to check).
Chris Wood quickly came to my rescue with replacement modulator chips which were duly soldered in . The device finally worked after an initial heart-stopping moment with no output before we realised that the DIP switches were not yet set correctly!
So yet another huge cheer for Frank C for this lovely design. Well done, sir!
-Jeremy
Jeremy. G8MLK. BVWS Chairman. British Vintage Wireless and TV Museum Friend.
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