Small LW receiver repair  - Page 1
Forum section: electronics / repair

author: Ubend
author_rank: Contributor
timestamp: April 24, 2025, 11:01:53 am
content: Total old noob here but would love to learn , so have decided to start with this receiver which is 9v and has a small transmitter and picks up 8-15 ft , I have two one is dead nothing and the other is only picking up half the distance , they have a on/off volume switch which I have tried replacing and swapping over etc , I am pretty sure they are LW as the transmitters can be picked up on some LW radios would love to be able to repair them or even one of them , who said you cant teach an old dog new tricks

author: Zenith
author_rank: Frequent Contributor
timestamp: April 24, 2025, 12:30:06 pm
content: Judging from the ferrite rod aerial, this doesn't look LW. I gather this is a transceiver, like a walkie talkie.People would be better placed to help if you said what make and model it was, and what the markings are on those chips, then it might be possible to find a circuit diagram, and a data sheet for the ICs, which is always a great help. A photo of the case would be useful.

author: Ubend
author_rank: Contributor
timestamp: April 24, 2025, 01:19:54 pm
content: its an old old unit and nothing on the chips etc , I used to use it to find drains etc , but now retired and looking for something to pass my time have always liked tinkering with things so thought I would try and repair this

author: Ubend
author_rank: Contributor
timestamp: April 26, 2025, 08:24:50 am
content: Any ideas anyone thanks

author: DaJMasta
author_rank: Super Contributor
timestamp: April 27, 2025, 06:00:34 am
content: With no chip numbers, schematic, or test equipment, you've got a hell of a mountain to climb for such a low part count circuit. Even a brand name could help, you're really starting quite disadvantaged without more information.If you can measure voltages and scope pins, you may be able to track down what portion isn't working. If you can map out how the board is laid out and reverse engineer a schematic, you may be able to find chips that have matching pinouts/functions and figure out what they were - and this is easier when you have a working one too.It's probably a better starting point to make a kit or design a circuit which can talk to it rather than repairing the broken one, but if you can figure out how it works, it could be as simple as adjusting the pots or trimmer cap to retune it.

author: Ubend
author_rank: Contributor
timestamp: April 27, 2025, 09:48:10 am
content: Quote from: DaJMasta on April 27, 2025, 06:00:34 ammany thanks for your reply but unfortunately all that is way over my head lol , I thought the one that is only working half the distance might just be a part needed replaced, and the dead one might be a capacitor or something , I was more hoping for a guide where best to trouble shoot etc remembering I am a total noob thanks again

author: MathWizard
author_rank: Super Contributor
timestamp: April 27, 2025, 10:22:18 am
content: So if the broken one doesn't drain a battery right away, how do the voltages compare between the 2 units ?With a DMM, you can compare as many things as possible, like the resistor values, caps, etc. You may want to remove the caps and check them, compare them (but yeah not all DMM's measure capacitance, but you can still check their DC resistance, which should be pretty high).Now if this was just a receiver, there would be lots of similar old AM/FM IC's, but yeah they may not have the same pin-out, or use the same external parts.

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 27, 2025, 10:49:33 am
content: It's a "Deben Ferret Finder", probably working at about 475KHz. Someone mentioned that the ICs are 4007 cmos ones but that could just be bs.No idea what the purpose of a ferret finder is, is it to find your ferret when it runs away?

author: Zenith
author_rank: Frequent Contributor
timestamp: April 27, 2025, 11:22:10 am
content: Quote from: PA0PBZ on April 27, 2025, 10:49:33 amWell spotted. It does indeed appear to be a Deben Mk1 Ferret finder. Trying Google, I couldn't find a schematic, but there are a few mentions of them, including repairers. A common problem is bad soldered joints, so resoldering suspect joints would be a good start.Quote from: PA0PBZ on April 27, 2025, 10:49:33 amThere's a collar that fits around the ferret's neck so you can find where it is in the rabbit warren. It might be a transponder. It's quite common for ferrets to eat the rabbits they are supposed to be flushing and then have a sleep. They can be valuable and if you want to recover them, it can involve a lot of digging. It saves a lot of work if you know where to dig.

author: factory
author_rank: Super Contributor
timestamp: April 27, 2025, 11:44:22 am
content: For the one that is dead, if there is no sound at all, it's possible the speaker could be open circuit, it does happen sometimes.The one that is quiet, it might be a capacitor problem, those small size capacitors can dry out & loose capacitance with age, but not always.The comment about adjusting pots, it would be very unwise to do this without marking position on the pots, that way you can return them back to the same position if needed.David

author: Ubend
author_rank: Contributor
timestamp: April 27, 2025, 12:56:34 pm
content: Quote from: factory on April 27, 2025, 11:44:22 amthanks I tried changing the speakers over and still the same but the speaker worked on the one thats not working , I was messing about yday with them and its powered by a 9v battery , I was getting a 9v reading at the speaker terminal on the one that wasnt working thanks again

author: GGMM
author_rank: Frequent Contributor
timestamp: April 28, 2025, 06:38:40 pm
content: hello,Out of curiosity I looked on the nettype "Deben Ferret Finder" there are many answers, even an electronic schema, youtube also...https://zorbaelbudae3kschematic.z21.web.core.windows.net/ferret-finder-circuit-diagram.htmlhttps://www.thehuntinglife.com/forums/topic/290027-ferret-finder-mk1-revision-5-need-your-help-i-will-return/page/2/etc, etc...cdt

author: Zenith
author_rank: Frequent Contributor
timestamp: April 28, 2025, 09:49:58 pm
content: I found those when PA0PBZ had identified this. There was supposed to be a cct diagram but I couldn't see it. It could have been I was using the wrong browser.It seems to be a 475kHz transmitter you put round the ferret's neck and a specialised receiver used to trace the ferret. The OP was using it to trace drains.They seem to be very well regarded of by the ferreting community, and the Mk 1 version is better thought of than later Mks. They fetch a tidy price on ebay in working condition.My idea is that they were produced by someone, who spent some time developing it, and realised he was onto a good thing in a small way, so he wasn't about to publish it as an article in an electronics magazine. He formed a company and sold this device. Good luck to him. He took the precaution of removing the ID of the chips after the first few were produced. The receivers are hand soldered and that seems to cause a lot of the problems.The company now refuses to fix these units, but a few people have reversed engineered the earlier versions and fix them for about £30 and also produce collars. The knowledge is kept close to their chests.It shouldn't be too hard to work out, given a basic oscilloscope, a cheap function generator and a bit of determination. The OP wants to have a go at this, to get into something new, interesting and rewarding in retirement. Does he have a multimeter?I think there are more approachable things he could take on as a learning exercise.However, some people seem to have made these things work by fixing broken circuit traces and resoldering dodgy joints, which is why I suggested it. A DMM with a buzzer and an electric soldering iron and solder would be handy.

author: Ubend
author_rank: Contributor
timestamp: April 29, 2025, 10:44:25 am
content: Many thanks for the reply , yes I only have the small part transmitter , and it was very accurate when working properly hence why I want to try and repair it I do have a DMM and a solder iron but as I said total noob wouldn't know where to start

author: Ubend
author_rank: Contributor
timestamp: April 29, 2025, 10:52:53 am
content: Quote from: GGMM on April 28, 2025, 06:38:40 pmThanks for the reply but the top link gets flagged as a dangerous site many thanks Jim

author: Zenith
author_rank: Frequent Contributor
timestamp: April 29, 2025, 04:21:56 pm
content: Have a look at this.It seems as he got his working by eyeballing it for bad joints, loose wires and broken circuit traces.By the looks of it they were hand soldered and not too well.

author: Ubend
author_rank: Contributor
timestamp: April 30, 2025, 08:59:05 am
content: Thanks again link not working here is a pic of the one that is only working half way the other is the same PS Its as it was when I got it tks

author: Zenith
author_rank: Frequent Contributor
timestamp: April 30, 2025, 09:19:55 am
content: Search Youtube using "Deben ferret finder mk1 repair" and you'll find it.Look it over. Check connections with your DMM on buzz range. Remake any obvious bad soldered joints. You may well find the problem.

author: PA0PBZ
author_rank: Super Contributor
timestamp: April 30, 2025, 09:36:23 am
content: Quote from: Ubend on April 30, 2025, 08:59:05 amTake out the speaker and check all the dark traces for continuity with your dmm. It looks like there was some corrosion, maybe leaked batteries.

author: Ubend
author_rank: Contributor
timestamp: May 02, 2025, 08:30:23 am
content: Well I took the speaker out bit of a pain to get at the terminals which are directly soldered to the board checked that corroded trace etc for continuity and all seems well , can anyone point out any components that could be suspect for being faulty many thanks

author: Ubend
author_rank: Contributor
timestamp: May 03, 2025, 10:46:33 am
content: Found this infoThe Deben device works remarkably well and can range between 1 and 10 feet. The system comprises a leather collared transmitter about the size of a sugar cube powered by mercury cells and a simple TRF ferrite rod receiver box with a gain setting 'range control'.It works on magnetic induction at about 150kHz which obeys a inverse cube law thus providing very sharp cutoff.

author: Ubend
author_rank: Contributor
timestamp: May 09, 2025, 12:30:34 pm
content: What would likely to be the suspect components in this unit thanks

author: Ubend
author_rank: Contributor
timestamp: May 11, 2025, 10:31:43 am
content: Think I am flogging a dead horse here , would this be time to admit defeat , cant help thinking it must be something simple , especially with the one that has lost half the distance , and the other was working when the were put away some time ago as it was my back up , thanks

author: coppercone2
author_rank: Super Contributor
timestamp: May 11, 2025, 11:10:44 am
content: Can it be the gain of an amplifier? Perhaps its low gain from age. I think those ancient transistors have that problem.The story about the ferret eating the rabbit and sleeping in the hole is totally hilarious btw. its like alien. Alien was right about that, they would use the xenomorph as a bio weapon, or send it to do manhole repairsI have no idea how it works but generally what you might wanna do is figure out how to feed a test signal into the thing. I don't know if you can do it, but for a amplifier I was thinking if you remove the antenna, and connect a signal generator, you can test the signal path to see if its being amplified and stuff. Though, I imagine its a weak signal.Though what I would do, is just flux all the solder joints and remelt everything. Like its a tiny amount of parts (and I sometimes do this shit on giant PCB when they piss me off and it takes days). Put way too much flux on it (like a drop), then solder it. Cherry picking them is for pros that have a good idea of what they are doing and need to save time. You don't need to save time to make sure the quote for a customer is reasonable.I have literarly seen a solder joint that looks 'ok' (shitty but people would say its ok, I would say it looked a little crusty) , but when I pull on the wire it moved! Don't pull on them, just remelt everything. If you have like 5000 solder joints to do, then you start 'thinking about it'. Old shit needs carpet bombing sometimes.Actually, it was the wire from a coil (enamel). See what I think is that to save time, if there is enamel that is supposed to be burned off (with solder), instead of tinning the wire first, people shove it into the hole and then solder it and hope it all goes to plan!!! they always wanna assemble cheap. It looks like you have a coil there that could theoretically have this problem.**some types of magnet wire (THE COPPER LOOKING ONE) are designed to be stripped in hot base, or mechanically cleaned with sand paper. Some are designed to be just heated with the soldering iron with solder on it to decompose the varnish (low temperature rating). Its easy to mess up removing the enamel. If its partially left on the wire, it could probably make a joint that fails later (i.e. very weak bond). I suspect it might in some rare cases be evil enough that when you press down hard with a multimeter probe (because the joint is crusty and you need pressure), it makes the circuit, so you never find it if you dont resolder, or at least have some gold probes. I never saw this though, its just a suspicion. But I definately seen bad enamel solder joints.If you have a 'burn off' enamel wire, which you are supposed to use the soldering iron to clean, and instead of doing it right and 'tinning' it on the bench, you just shove it into the hole and solder it... then you never inspect to see if the enamel actually is gone (if its ready to be soldered) and you just hope it goes to plan inside of the hole.For remelting you should use alot of flux and agressive flux (rosin mildly activated or better rosin activated (but you must clean). The modern hip fluxes are meant for nice circuit boards. I like it when a big glob of flux boils on top an old solder joint and cleans it up niceIf you do that, since you don't have alot of parts, you can carefully desolder the resistors and measure them out of circuit to see if they all agree with what they are supposed to be. The foil capacitors can be measured with a LCR meter. Then you are left with three chips and have a 30% chance of repairing it with each replacement.I had another repair like that, where they had a rivet with a cracked solder joint. When I probed it, it measured ok, but when I took the probe off it went screwy. I did the process where resolder maybe 10% of the PCB and turn it on again to see if anything changed. I happened to solder the rivet in one of these cycles, and it worked.

author: coppercone2
author_rank: Super Contributor
timestamp: May 11, 2025, 11:39:22 am
content: Those potentiometers can go screwy too. Best to replace, 2nd best is to take apart, ultrasonic clean and grease, 3rd best is to try to get some deoxit in there and traverse it back and forth a few times to clean it up. But you would need to know how to tune it. Definatly check the resistances on them.

author: seanf
author_rank: Contributor
timestamp: May 11, 2025, 11:40:01 am
content: Quote from: Ubend on May 11, 2025, 10:31:43 amHave you looked into "Makerspaces" or "Mens Sheds" or similar in your area? some of them will be involved in electronics.https://www.facebook.com/groups/GlasgowMakersAndHardwareHackers/?locale=en_GBhttps://scottishmsa.org.uk/Your profile says your in Glasgow? Maybe someone on here may have a suggestion on a place to try?

author: coppercone2
author_rank: Super Contributor
timestamp: May 11, 2025, 11:48:39 am
content: and electrolytic capacitors are responsible for like 30% of the problems in the worldalso wash that board. Bateries do all kinds of weird shit. Mercury batteries I don't even know about. I know mercury can infiltrate aluminum

author: coppercone2
author_rank: Super Contributor
timestamp: May 11, 2025, 12:00:30 pm
content: And for cheap shit and those generic transistors, you could try a diode test. Do diode test on both units and see if they match up. Perhaps you find discrepancy and can build 1 functional unit from 2 units.google how to test transistors. in circuit works sometimes. fets are a bitch but BJT are nice. Best if you desolder them, but you can still find discrepancy in circuit if one does something much different then the other one.lol unless its some evil shit like a UJT, thyristor and god knows what. But if its an amp maybe its just 3904 and 3906 (easy street)

author: Ubend
author_rank: Contributor
timestamp: May 11, 2025, 02:11:44 pm
content: The Deben device works remarkably well and can range between 1 and 10 feet. The system comprises a leather collared transmitter about the size of a sugar cube powered by mercury cells and a simple TRF ferrite rod receiver box with a gain setting 'range control'.It works on magnetic induction at about 150kHz which obeys a inverse cube law thus providing very sharp cutoff.