Products > Test Equipment
FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
DaveR:
I had a spot of trouble with my FY6600 over the weekend, when C82 blew and took the -12.5v rail down to -1.25v. It happened while I left it running as I went into the garden for ten minutes, and I got back inside to find the scope display scrambled, and the mains transformer and LM337 regulator very hot instead of their usual slightly warm. I can't see any reason for C82 going bad other than it being just a faulty capacitor (which turned into a 63 ohm resistor), but fortunately it doesn't seem to have caused any damage to anything else, as all is fine again with a new cap in place. Maybe it would have been a different story if I was still using the original power supply?
Whilst using Der_Kammi's schematic to trace the fault (C82 is one of the 100nF bypass caps to the IC5A/B op amp, half-under the heatsink on the main board), I noted that the schematic shows IC5 as a JRC 4558DD, whereas my v1.501 board has a JRC 4556A there. From the datasheets it looks like the 4556 is something of an upgrade over the 4558.
Soundtec - thanks for the Wavemanager 4.1 tip: I've downloaded it, but haven't tried it out yet.
Regards,
Dave
bugi:
--- Quote from: DaveR on August 13, 2018, 10:19:43 pm ---... I can't see any reason for C82 going bad other than it being just a faulty capacitor (which turned into a 63 ohm resistor), ...
... (C82 is one of the 100nF bypass caps to the IC5A/B op amp, half-under the heatsink on the main board), ...
--- End quote ---
Would that C82 happen to be an ordinary cheap ceramic SMD? Under a supposedly hot spot? Perhaps uneven thermal expansions, ceramic or its ends breaking, leading to a broken cap? (Certainly the cap could have been bad to start with, or partially damaged from e.g. soldering process, add some extra stress later...)
DaveR:
Yes, the very same ultra cheap SMD, but it wasn't actually under the hot spot - which isn't that hot anyway - so thermal stresses would have been minimal. Under the magnifier you can see that a groove has been burned across one face, and one end is brown and pitted (which is what caught my eye initially). Just bad to start with, or a bad soldered joint, probably. I'm waiting to see if its twin, C81, blows as well, as I've now got 49 spares to replace it with :)
danco:
Hi guys, I,ve been reading this thread all from the start, in the meantime my fy-6600 has arrived, v.3.3. First thing, even before testing it thoroughly, I was swapping the 3002 with 2 pcs. 3091 I bought from aliexpress. All seemed fine until recently I got time to play a bit with it and found that over 5V level a relay made a "click" and the signal at the outputs vanishes. In fact, channel 1 outputs a -11.7V DC, channel 2 outputs 0 V. Consulting the schematic I see that the final stage is switched in by a relay (most likely over 5 V output amplitude) so I think both my aliexpress chips are dead. Switched back to the original 3002 and everything back to normal (in certain limits). Can anyone confirm all this is plausible or I could have made something wrong myself? The chips look genuine, came in original tape cut, but were only $2.79/piece. Any thoughts?
bdivi:
The THS output is switched for signals over 5V so your assumptions is correct. Most probably the aliexpress parts are a dud.
I decided to go for the TI's original THS3491 which cost me $10 a peace direct order - $20 total with free shipping.
The have been working perfectly so far.
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