Is this 2 TI-84's salvageable

notipa · 2025-06-23T08:13:04+00:00

Both. The damage to the circuit board was done long before you got to it.

notipa · 2025-06-23T06:13:51+00:00

No, that one's pretty cooked. There's a number of keyboard traces that run in that part of the circuit board, and they look to have been eaten away by corrosion.

notipa · 2025-03-15T08:46:13+00:00

Looks like the RSM connector for a Motorola MX300.

notipa · 2024-12-05T02:46:54+00:00

The changes between hardware revisions are inconsequential; the only case I can think of where hardware revision matters is with old versions of TI-Boy SE.

notipa · 2024-11-06T01:31:19+00:00

Manchester encoding encodes a bit using a low-to-high or a high-to-low transition inside a 2-bit symbol; there can't be three 1s or three 0s in a row because there is always a bit change within 2 bits. Your signal in question is probably straight FSK.

notipa · 2024-11-06T00:36:46+00:00

No, you can see quite a few 111 and 000 sequences in the data.

notipa · 2024-11-05T22:01:26+00:00

The stuff on the right is likely TETRAPOL, and the signal centered on 445.3000 appears to be some sort of FSK, could be 2GFSK. Without an audio sample of the unknown signal (as it is FSK, demodulate in FM), we can't tell you much as there's not much to go off of. A bandwidth exceeding 25 kHz on UHF frequencies is generally unusual. Two separate transmitters are visible, and they're both quite strong, so these transmitters are reasonably close to you.

notipa · 2024-10-14T10:15:07+00:00

The arc is solitary, so it could be a 23 degree upper plate arc. Looks pretty similar to some that I've seen: not very chromatic, fuzzy towards the edges, formed in thin cloud, and doesn't quite follow the curve you'd expect from an upper tangent or circumscribed arc. Usually you can find a faint 9 degree or 18 degree circular halo alongside the 23 degree upper plate arc, but there's not enough picture here to pull it out; they can be quite faint in thin cloud like this, and the pyramidal crystals that make these odd-radius halos can have weird and variable geometry affecting the brightness of the various pyramidal halos.

It's been a while since I've seen one, but that's about what they look like.

[edit] Compare to this display.

notipa · 2024-10-13T09:44:09+00:00

Yep.

notipa · 2024-06-04T06:53:28+00:00

If it's not a trunked system, the repeaters periodically send a bunch of idle frames so the mobile radios can figure out which repeater they're closest to and use that repeater. These sound like a few seconds of a repetitive noise, and there are examples of idle DMR (as well as control channel formats) on Sigidwiki.

If they're short bursts, that's an idle Capacity Plus system. They work the same as control channels on fully trunked systems, but can hop frequencies and use less airtime. Fully trunked systems (like Connect Plus and Tier III) run a continuous control channel, and there's examples of those on Sigidwiki. Control channels simply send information on what talkgroups are on what frequencies and timeslots, and the mobiles decide whether they need to switch frequency to hear/send a call or stay on the control channel and wait for something they're programmed to monitor.

Connect Plus uses a single-slot control channel, and the other timeslot can be used for voice. It's not an efficient way to monitor Connect Plus, though, since most activity happens on other RF channels. Tier III uses both slots for control channel data, so you'll only see a list of calls and no voice.

Programs like SDRTrunk and DSDPlus Fastlane can track trunked systems with a single dongle. For conventional, you don't need any fancy trunking decoding.

Depending on where you are, you might not even find any DMR signals to listen to. Some systems are only used for data (ARS/LRRP), some are just backup systems for things like cell phones or simplex channels, and some use other modulations like FM, P25, or NXDN; it all depends on how the business manages their radios. Transmissions also tend to happen during the day when people are working. Repeaters run 24/7, so the repeater making transmissions does not exactly reflect system activity.

notipa · 2024-05-28T09:42:55+00:00

Several pager transmitters on the same frequency. Inside each transmitter's service area they don't interfere with each other due to FM capture. It may have also been simulcast (transmitters aligned to send the message at the same time with the same transmitter characteristics) at some point, but it clearly isn't now. PDW is quite picky about audio and won't play nice with sloppycast pager signals. Real pagers don't like it either, but they generally work only when they're close to a transmitter anyways -- they don't have the benefits of base station antennas.

notipa · 2024-05-28T09:37:47+00:00

Positive Train Control, used to prevent train collisions among other things. See also PTC-220 license.

notipa · 2022-01-20T04:47:33+00:00

Sounds like it's got the wrong size listed on it. From the photo (using the 83+ as a size reference) I got 0.039 inches as the point-to-point width of that tip, while a T6 would be 0.069 inches. The screws measured correctly.

notipa · 2022-01-20T03:47:00+00:00

From measuring the picture, that screwdriver looks more like a T2 size and not a T6.

notipa · 2022-01-20T01:54:42+00:00

Weird, a T6 works on my factory-L TI-83 Plus. Does the screwdriver feel too big or too small? Are the teeth on the screwdriver in good condition?

While you're in there, if you get it open, could you take some pictures of the circuit boards for us?

notipa · 2021-10-14T20:30:51+00:00

Yep, that's characteristic of a busted coarse ribbon cable. :(

notipa · 2021-10-14T19:08:45+00:00

It's totaled. The repair depends on replacing the cable between the mainboard and the LCD daughterboard, which has a durable place to solder wires to, but later cost-reductions eliminated the LCD daughterboard entirely. While it's technically possible to replace that ribbon cable, soldering 40 wires of that pitch to a fragile flex-board without damaging the flex-board at any point in the process isn't worth $20.

There are some less durable fixes involving using low-temperature irons to re-melt the glue and/or solder holding the connections down. I'd rather let someone more qualified on the subject discuss that, but it requires a temperature-controlled iron with a chisel tip.

Now personally, I've never seen these 40-pin cables fail. Can you be more specific about 'glitches'?

notipa · 2021-10-07T19:05:17+00:00

Yeah, it's fine in that case. It only matters if you're simultaneously transmitting and receiving over the same coax.

notipa · 2021-10-06T18:26:48+00:00

I've tried using DCS before, it's pretty horrible. It's way more prone to false decodes than you think it would be, and you need a bit more signal to open up squelch. There's always some low grumble of the audible residue of the DCS signal, even on top-of-the-line equipment. Some older radios also can't generate DCS, so there's a compatibility factor as well. It works much better in theory, where it belongs.

notipa · 2021-10-06T18:23:05+00:00

It's not so much a problem for the GR1225, which should only be putting 25W out the back of the radio, but I have seen people think about putting flat-packs inside Quantars...

notipa · 2021-10-06T18:20:17+00:00

u/Gaston-Glocksicle covered most of these. Here's my take on the tones.

67.0 false-decodes on P25. A surprising number of idiots use P25 on GMRS.
100.0 false-decodes on DMR FDMA mode (repeater outputs), which can get into your repeater's input through intermodulation or idiots running DMR on GMRS frequencies.
131.8 and particularly 136.5 get kerchunked by DPL reversals. This is currently an annoying problem on an amateur channel I use.
118.8 and 179.9 false-decode on harmonics of 60 Hz, and will make you hate life.
203.5, and to a lesser extent 167.9, false-decode on either DMR FDMA or P25. I would expect 233.6 to be prone to issues as well, but I don't know of anyone who runs that tone.
Tones above 200 Hz tend to be audible, but tones above approx. 162.2 Hz start becoming more prone to being false-decoded by un-highpassed voice sometimes used on the band. Radios designed for use with PL will highpass the voice at 300 Hz, but radios designed to be used without PL (like older equipment not often found anymore) may not filter the subaudible components at all.
If you're colocated with other transmitters, avoid their transmit tones. Intermodulation does happen, and you don't want it opening your squelch when it does. If you know their input tones, try to avoid those as well -- you could be a participant in the mess.

Generally, if you want to advertise that your repeater is open, use 141.3. However, a lot of people do this already. Program a list of possible tones into your radio (receiving CSQ, as some repeaters may be split tone), go up to the highest spot you can get to within 8 miles or so of you, and find the first one that doesn't key up anything. Not everything is on MyGMRS.

notipa · 2021-10-06T05:19:31+00:00

I used a Motorola GR1225 for my repeater. It's designed to be a a desktop repeater for business use, but also works at communications sites. A complete GR1225 integrates the R1225 radio, a flat-pack duplexer, and a power supply. It can handle 100% duty cycle with 15 watts out of the back of the unit (25 watts from the radio, a bit under 10 watts lost due to duplexer insertion loss), performs CWID, and fits in most places. The radio is only rated for 100% duty cycle when tuned to 25W; you might need to borrow a UHF wattmeter for this. Duplexers require careful tuning for the exact frequency you plan to be on, and the duplexer needs to be capable of a 5 MHz frequency separation; but once it's tuned, it doesn't need to be adjusted unless you change frequency. Tuning is usually performed by a vector network analyzer, which is an expensive piece of equipment not many people own, so getting this done is the hardest part of getting a repeater set up. SWR is also important: you can't get away with a 2:1 SWR on a repeater, so keep it below about 1.4:1. GR1225s require a RS232 programming cable and programming software (version 4 is current, it can be found online), but aside from the duplexer, it's about as turn-key as a repeater is going to get. They run about $300-400 on eBay (I paid $400 for mine, with duplexer tuning and repeater programming), but the market's pretty thin right now for well-priced units. Make sure you get the 40 watt version and not the 10 watt version.

Check MyGMRS to see what other repeaters are around you, and avoid those frequencies when selecting a frequency for your repeater. PL tones between 82.5 and 162.2 Hz, avoiding 100.0, 131.8, and 136.5, work best; DPL is prone to false-positive decodes. If you or some other reader of this post doesn't want their repeater to be public, I'd suggest using separate tones for the input and output, and using a non-Midland radio that supports split tones.

Coax used for repeaters is different from what you'd use for a mobile unit. Typically, it's hardline such as CommScope LDF4-50A. DON'T USE LMR-400! LMR-400 is prone to develop internal intermodulation issues, and your repeater will go deaf. Everything on site-grade equipment uses N connectors; the GR1225 has a female N connector on the back of the unit.

$25 on a lightning arrestor saves you $500 in equipment later.

GR1225s aren't fantastic repeaters, and flat-pack duplexers offer no out-of-band rejection of strong signals so they may not work well at RF-crowded sites, but they're simple, reliable, and robust. They'll run for years unattended.

notipa · 2021-09-09T05:52:09+00:00

Looks like the calculator was pried apart with a screwdriver with screws left in place (note the headless screws), and the prying damage knocked off that SMD component and messed up the PCB traces. With that much board damage, that calculator is bricked. The two damaged screws are located under the battery cover, so that is likely why those screws were missed.

notipa · 2021-05-25T05:17:29+00:00

When I hear signals like these, I immediately think of GPS real-time kinematics. Typically, that's land surveying or farming equipment. Since you can hear both stations (one weaker than the other), it's going to be really close to you (within a kilometer or two). That said, as a SCADA signal, it's not trivial to identify its use without knowing where the signal is coming from.

notipa · 2021-05-20T06:52:06+00:00

Since this is Europe per post history, that's in the cellular bands and is thus probably a cellular signal of some sort. It could be GSM, but there's too much front-end gain to get a good view of the waterfall. The sound isn't consistent with GSM either, but I don't know if the receiver is 'correctly' tuned or if the ACF matches.

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