USS Marlin, lost..... then found 231 days later

[Ken_NJ]

Bob doesn't have CH77. I did find a transmitter crystal on CH65 on Amazon.

[Ken_NJ]

Thanks David,

Looks like I'm partly in luck. The Xmitter is PPM and both receivers Bob sells are PPM. I'm limited by the SD diameter which is 2-3/8 or 60mm so either one should fit even with the plugs coming out the end. The regular one is 48mm without the case and the mini one is 40mm without the case. Just need to find out if he has CH77. Will post in his Product forum.

[He Who Shall Not Be Named]

Sorry never got back to you guys. Here is what I tried. Soldered the original antennae onto the receiver. Tested, same problem, loss of signal about 75 feet. Tried coiling the antennae around a dowel. Still LOS. Resoldered the receiver antennae connection. Still LOS. Opened the transmitter to check the antennae, it connects to a machine screw which connects to an L bracket, I loosened and tightened the nuts. Still LOS.

I had two receivers with this transmitter which was reserved for using with subs. The first receiver did this same thing, LOS about 50-70 feet. I checked with Tony at RC South and Hitec, they both said no parts are available.
I was using the second receiver in the Marlin. I bought this off of eBay, NIB, at 72 Mhz. I sent it tony Tony years ago to have him tune it for 75Mhz and been using it ever since. Now this one crapped out.

Any ideas what now?

The radio is on 75.730 CH77 and is a Hitec Laser 6. Both receivers are dual conversion. Will any of Bob's single conversion receivers work if I can get the same frequency? Pressure is on me. If I don't get this resolved its not worth going to Groton as I won't have a working sub.

A single conversion crystal that is FM and on that channel will work just fine, Ken.

The only variable is the receiver and crystal as far as single or dual conversion goes. If the detector circuit of the receiver (the input, or 'front-end') is single or dual conversion, then you need a single or dual conversion crystal -- even though both types will state the specific frequency/channel (let's say, ch-77) on the crystal. The transmitter, as long as it's FM, does not give a whit how the receiver processes the signal, just as long as the intelligence sent from the transmitter (the pulse train, which is encoded as variations of frequency) matches the decoder logic of the receiver.

Dual conversion receiver must use a dual conversion crystal, single conversion receiver must use a single conversion crystal. Transmitter don't care!

One fly in the ointment -- the transmitter encoder logic must match that of the receiver decoder logic. Today it's either PCM or PPM. Make sure your receiver and transmitter share the same encryption type.

Snatch up a new receiver from Bob -- all he sells now are FM types, and they come with crystal installed. Tell him what channel your transmitters on, maybe he can find a receiver already on ch-77 for you.

If Bob can't get it to you right away I can rip a receiver out of an inactive boat and loan that to you. Finding one on ch-77 will be a problem though. Is your transmitter Futaba crystal compatible?

Hope I did not throw too much **** at you at once, Ken. Keep posting, pal. We'll work this out.

We'll get you back into the water. No excuses!

David

[Ken_NJ]

Sorry never got back to you guys. Here is what I tried. Soldered the original antennae onto the receiver. Tested, same problem, loss of signal about 75 feet. Tried coiling the antennae around a dowel. Still LOS. Resoldered the receiver antennae connection. Still LOS. Opened the transmitter to check the antennae, it connects to a machine screw which connects to an L bracket, I loosened and tightened the nuts. Still LOS.

I had two receivers with this transmitter which was reserved for using with subs. The first receiver did this same thing, LOS about 50-70 feet. I checked with Tony at RC South and Hitec, they both said no parts are available.
I was using the second receiver in the Marlin. I bought this off of eBay, NIB, at 72 Mhz. I sent it tony Tony years ago to have him tune it for 75Mhz and been using it ever since. Now this one crapped out.

Any ideas what now?

The radio is on 75.730 CH77 and is a Hitec Laser 6. Both receivers are dual conversion. Will any of Bob's single conversion receivers work if I can get the same frequency? Pressure is on me. If I don't get this resolved its not worth going to Groton as I won't have a working sub.

[trout]

Bob, that is also a good suggestion! I had that on a F-14 TX unit.

[Bob Gato]

I had a problem with a surface boat, and 75 ft was about all I could get (Note this was a new 2.4 MHZ radio) In desperation, I opened the transmitter and found the antenna wire had become disconnected from the PC board-reconnected it and I stopped the walk test at 1/8 mile!

[Ken_NJ]

Worth a try. Will give it a go on Tuesday.

[trout]

Looking all sorts of pretty......
You cut your receiver antenna? As a last resort. Replace your antenna on the receiver - coil it on a plastic rod. This will be self contained in the WTC. Now here is some heretic stuff......There is a gentleman who has been in the hobby for a long time that said do not cut the antenna, just leave that length and attach it to the additional exterior antenna. I did this on one sub and it worked amazing. I know what some will say about attenuation and wave length, but if you are up against a rock and a hard place.....you might give it a try.

[Ken_NJ]

Tested the boat in the bathtub. Everything seemed OK. Tub was not long enough to fully submerge, damn. Tried in a pool, submerged to about one inch below top of the sail. OK there.

While running in the pool (freshwater pool) she seemed at some point to loose the signal, the motor stopped. If I moved the transmitter closer she started again. This happened on and off.

The next day ran the boat in different builtin pool (freshwater), same problem. Once I moved closer, the boat started responding on and off.

Today I had the SD in the driveway, left the motor running and walked away from it with the transmitter. When I was about 75 feet away the motor shut down. If I moved around at that distance the motor would stop and start. Someone suggested to coil the antenna, tried that and tested again in the driveway, same problem. This is the second Hitec receiver for this boat that exhibits this problem. The first receiver this happened to I ask Tony at RC South and he said he doesn't have the parts to repair the model receiver I have. Any ideas guys? I hate to think this is the end of using this radio.

[Ken_NJ]

Been hard at work getting things back together. Some pics...









Non working things

[Ken_NJ]

For the replacement batteries I removed the positive metal tab, then tinned the negative ends.Glued the batteries together singly with silicone and positioned them in the SD so they keep the curved shape of the tube and align the metal tab with the next positive terminal. Once the silicone dried, I trimmed the negative tab, sanded and fluxed it then soldered the tabs to the respective positive ends. At this point I charged the complete pack. Once charged I soldered the magnetic switch and tested everything. All works like a charm! Didn't see any need to change anything from how I did it before. Each battery is 3800ma. Never had a problem soldering tabbed batteries like this. Now that the batteries are ready, onto the electronics package.

[Ken_NJ]

My original clear coat was a Rustoleum Flat or Matt clear and it had some whitish spots that appeared after a while. Might try Dullcoat on the lower hull to see what happens. Most likely will wait until the fall before I decide anything.

In the meantime have new batteries and new electronics tray with a non rusty motor and LPB. Out with the old and in with the new.



Have lots of small parts to put back together. My goal is to have this ready for July 26th when we will be running models at a local YMCA camp for kids in their 75x75 foot pool.

[DMTNT]

I'd spray with Dullcoat looking at the pics you've provided. Personally I found that the ultra-matte finish left weird water staining on my boat if I didn't completely dry it as soon as I pulled her from the water. I sprayed on a Rustoleum Acrylic Matte, which admittedly is more of a semi-gloss. The result is a boat that's a tiny bit shinier than I'd like, but that behaves well when it gets wet.

[Scott T]

Glad to hear from you and your recovery is going well.

[Ken_NJ]

Sorry for the disappearance. Had to get a planned aortic heart valve replacement. Been 2 months on July 10th, doing great with recovery!

Bob, thought of using Coke, should have tried it.
Thanks Brady, still up in the air what I'm going to do. Will leave it as is until after Groton in September.

Using 5000 grit paper gave the paint surface a shine which I'd like to remove. Removing the grime also thinned out the flat clear coat and I damaged some of the decals. I can either leave as is, not sure if sanding with courser paper would remove the shine or spray with Dullcoat.

The batteries were shot, I used NiMH, already ordered replacements. The drive motor or gears were frozen and after some muscle I got them moving and the motor now runs, but the motor can is rusted and don't know what it looks like in the motor. The LPB is also rusted and the PCB had some pitting. Did not test it out yet. When David reads this I did shoot you and email about the drive motor and LPB.

The ADF2 and ESC are both fine. There was about 2 tablespoons of water that seeped into the SD that caused the rusting. Not sure how it seeped in after 231 days.