Hello everybody. First post. If I do or say something stupid, please don't shoot me on sight.
Same about grammer errors : non-native English ect ect.
Here's a friendly warning to all CB88 owners : mine developed a very nasty failure yesterday after roughly 4000 bb's shot over a period of about a month.
A big THANK YOU to RedShirt for posting about this gun, and reporting the massive powerdrain of the gun when switched off. I've no doubt this warning has saved me more than 1 battery so far.
I also agree on his opinion that the inside of the CB88 isn't badly made at all. I've seen comparable AEG's from the inside, and compared to them the CB88 has been made with some TLC that's for sure.
HOWEVER.
If you fire your gun even for short bursts, inspect if you smell a typical "heated electornics" smell, roughly right above the battery compartment. If you do : read on. If you don't, might as well read on too.
While the mechanics of my gun were made pretty neat, the trigger/electronics board that resides just above the battery compartment was not. In fact, I believe it was soldered by a 8-year-old boy or girl in some sweatshop. The board is riddled with cold joints, wires are/were very badly soldered too. But worst of all, the rectifier (a TO-220 Mosfet part - IRFZ44n ) was either too badly soldered, or it was a fake IRFZ44n running lower specs than should be.
What happened :
After sighting in a laserpointer and firing off 40-or-so rounds in SF mode, the gun "took off" and went full auto _WITHOUT HAVING A FINGER ON THE TRIGGER_. I was so caught by surprise it took me a second or two to understand what was happening. I pulled out the mag, but the gun just kept spitting out the bbs still in the feed tube. I snapped out the battery holder and disconnect the 7.4 Lipo. ... so the gun stopped and went dead. And stayed dead after reconnecting the battery a minute later after a fast external visual inspection didn't immideatly show a reason for this behaviour.
After opening the gun, it turned out the IRFZ44n chip not only did fail, it failed catastrophically, it soldered itself OUT of the control PCB and in super-hot condition had caused a shortcircuit on the 9V line as the part had become so hot it litterally melted the 9V wires. There's a blob of hotglue at the rear side of the gun that fixate the 9V wires : the IRFZ has melted the hot glue and had fixated itself again on that position.
I've replace the IRFZ44n with a IRFZ48n now : not because I think the 44n shouldn't be more than strong enough to cope with the current draw of the CB88's motor, but because I couldn't find that 44'er in short notice. The 48 is pin-compatible, but it can draw a higher current. I now knew why the gun smelled so funny after firing even just a couple of rounds : the middle pin of the 44'er had turned blue-ish (typical sign of massive overheating).
As said, I replaced the 44n with a 48n, but also provided a small TO-220 compatible heatsink to make sure this issue wouldn't read its ugly head in the future. I also resoldered about 80% of the small PCB as the soldering quality was really sub-standard. The PCB only carries a small SMD chip, some passive SMD components, the IRFZ44n and some connectors, so that was done in a couple of minutes of time. I also replaced the fried 9V wires and refixated the stuff.
After that, the gun came back to life and I carefully reassembled it (note : the two side-LED's are really fragile in terms of soldering too ... one of them broke TWICE while reassembling the gun).
So the gist : if your gun smells funny after even firing of 20 or 30 rounds, you might be on your way to a similar situation. The good news : it's easy to fix. The bad news : you'll have to open the gun.
Anyhow, after opening the gun, I'm quite sure I'll make some additional modifiations (a better flashlight, possibly a combo flashlight/laser dot) and some kind of deadmans' switch to prevent "run away" firing in the future for sure by automatically disconnecting the main battery when not being used to fire. (maybe a pressure switch in the stock, but that would mean the gun can only be fired when being shouldered .... not to happy about that. If anybody has a better idea : shoot
).
Hope this info will be useful to some of you guys someday because as it stands, our CB88's won't be easy to replace if they'd break down. For all I know this might be a batch problem, or maybe I'm the only one. Can't say.
But it's a good thing the overal construction of the CB88 is pretty good and repairs are pretty easy to carry out.
If you've got any questions about this : just ask. Till then happy shooting !
PS : actually, it should be pretty easy to implement a switch that disconnects the main battery whenever the gun is put in safety : that would be the more elegant solution. If there's any interest in this, I'll do a small update on this when I do it.
