Is your current USB to serial adapter an entire cable? For example, one side is 
a USB plug and the other is a DB25 male plug? With no other parts in between 
the two?

Kurt

On Wed, Apr 10, 2019, at 9:54 AM, Thomas Morehouse wrote:
> Thanks Kurt. But we already know that my current usb/serial adapter (which is 
> a single unit usb/serial cable) cause the 102 screen to dim. In other words, 
> that's where the problem is.
> 
> So I don't see how a new null modem cable plugged into my faulty usb/serial 
> adapter/cable will help the situation.
> 
> Tom m.
> 
> 
> On Wed, Apr 10, 2019 at 12:51 PM Kurt McCullum <[email protected]> wrote:
>> __
>> Tom,
>> 
>> The cables that Brian is recommending will attach to your existing usb to 
>> serial adapter. So the connection would work as follows. 
>> 
>> Laptop USB Port -> USB to Serial Adapter -> DB9 to Db25 Null modem Cable -> 
>> Model T
>> 
>> Kurt
>> 
>> On Wed, Apr 10, 2019, at 9:46 AM, Thomas Morehouse wrote:
>>> Thanks Brian. Turns out your cable links weren't in my thread at all. They 
>>> were in a different thread completely which I wasn't part of, and wasn't 
>>> following.
>>> 
>>> Here's the situation. Those two cables you recommend in that other thread 
>>> are null modem cables. Fine - but I've already learned the problem I have 
>>> is with my usb/serial cable. Soon as I plug it into the 102, the 102 screen 
>>> dims, which may be caused (I've been told) by crossed wiring in that cable.
>>> 
>>> So, even if I do buy another cable (one of the null modem cables), I'd 
>>> still need some kind of usb/serial "converter/adapter". There's no usb on 
>>> the recommended null modem cables, and there's no serial port on the Dell 
>>> laptop or desktop.
>>> 
>>> Thanks.
>>> Tom M.
>>> 
>>> 
>>> On Wed, Apr 10, 2019 at 12:39 PM Brian White <[email protected]> wrote:
>>>> In one post, I provided a link directly to two items, a specific cables2go 
>>>> cable and a specific sabrent usb-serial adapter, so that you wouldn't have 
>>>> to make sense of the full page where that info came from.
>>>> 
>>>> And also linked that full page, which includes the startech and others.
>>>> 
>>>> http://tandy.wiki/Model_100_102_200_600_Serial_Cable
>>>> 
>>>> I know reading that full page might not make 100% sense, because it's a 
>>>> lot of verbiage, and there are many cables listed there and they all work 
>>>> for this so how do you choose, and some parts are kind of cryptic, which 
>>>> is why I pulled out the two parts to get.
>>>> 
>>>> For instance the shorthand I used to document each cables wiring 
>>>> idiosyncracies, like "DCD<>DSR+DTR", I know that part is cryptic. When I 
>>>> was testing cables and assembling the info, I just needed to get the key 
>>>> details written down, and the form didn't matter. I could expand it to be 
>>>> more readable later.
>>>> 
>>>> What those little things are showing is how each particular cable differs 
>>>> from the rs232 spec.
>>>> 
>>>> For instance "DCD<>DSR+DTR" means that dsr and dtr are tied together on 
>>>> one end, and connected to dcd on the other end, and that it's the same on 
>>>> both ends in both directions. All other connections are according to the 
>>>> rs232 spec, and you get the pin numbers and positions from the rs232 spec.
>>>> 
>>>> Some time when I want to spend more time on that page, I can expand those 
>>>> to a less cryptic form, (or anyone else can, it' s a wiki) but until then 
>>>> at least the knowledge is documented so that later I can refer to it. It's 
>>>> sort of like working notes until then.
>>>> 
>>>> Mike Stein also provided a direct link to a specific monoprice cable. That 
>>>> one is good too. (it's on that page too for instance)
>>>> 
>>>> All other cables you randomly find from wherever, probably aren't right 
>>>> without some kind of adapters, and there is no way to tell if the wiring 
>>>> is right except by knowing the rs232 spec and testing the connections.
>>>> 
>>>> rs232 is not a single thing, it's a spec with a bunch of options and 
>>>> configurations. In order to use anything serial, you the user, actually 
>>>> has to understand that spec, or, you have to take the word of someone else 
>>>> who does, and says "this specific cable will work for this specific 
>>>> application". Plugging in any old cable without knowing how it's wired or 
>>>> what the different rs232 signals are for and how they work, will never 
>>>> work. Serial is not like usb or ethernet or headphones.
>>>> 
>>>> For another example of ehat I mean, even when you finally get a correct 
>>>> serial cable for connecting your m100 to a pc, that cable won't be correct 
>>>> for connecting to a modem, or a plotter, etc. 3 different devices, 3 
>>>> different cables, and yet all of them are valid correct serial cables even 
>>>> though they are all different from each other.
>>>> 
>>>> The only way to make it work is to understand that and go read about 
>>>> serial cables so that you know enough that you could build your own from 
>>>> scratch, or continuity test any off the shelf cable to fully understand 
>>>> what it does. Or, buy one that is already known to be correct for this 
>>>> particular task.
>>>> 
>>>> -- 
>>>> bkw
>>>> 
>>>> 
>>>> 
>>>> On Wed, Apr 10, 2019, 7:30 AM Thomas Morehouse <[email protected]> 
>>>> wrote:
>>>>> Brian - you wrote:
>>>>> 
>>>>> "
>>>>> 
>>>>> The Cables2Go one I linked is all the same, except it also has rts/cts, 
>>>>> so it works with HTERM, as well as everything else.
>>>>> 
>>>>> And finally, the StarTech one I linked, is also all the same, but 
>>>>> without shorting DCD to DSR, or shorting DTR to DSR, which means that 
>>>>> one should cause the least possible drain on any possibly weak power 
>>>>> rails in the M100.
>>>>> 
>>>>> All this mystery has already been completely figured out and nailed 
>>>>> down. One mouse click and $7 later and you're done."
>>>>> 
>>>>> I've gone through all your posts in this thread, and find no links for 
>>>>> Cables2go or StarTech.
>>>>> 
>>>>> I'm absolutely going nuts here, trying to figure out how to do things, 
>>>>> and how to follow advice. One post with advice raises a question, someone 
>>>>> else tries to answer the question, then someone else tries to clarify the 
>>>>> answer to someone else's question. Really helpful to some, but 
>>>>> frustrating to me.
>>>>> 
>>>>> Which post had those two links for the proper cables? I've now got two 
>>>>> usb/serial cables which don't seem to work, plus several male/male, 
>>>>> female/female, and DB9 to DB25 adapters. Total so far: $100.
>>>>> 
>>>>> As I can't find the links Brian referred to, I don't want to guess and 
>>>>> buy yet another thing which might not work.
>>>>> 
>>>>> Thanks.
>>>>> Tom M.
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> On Tue, Apr 9, 2019 at 9:34 PM Kurt McCullum <[email protected]> wrote:
>>>>>> __
>>>>>> Tom,
>>>>>> 
>>>>>> Looks like you will need to either build or buy a cable. My two cents is 
>>>>>> below but I'm sure others will chime in. There are several options out 
>>>>>> there.
>>>>>> 
>>>>>> Here is a description of what I do with all my Model-T units. I start 
>>>>>> with this DB25 to DB9 adapter which is just a regular DB9 to DB25 
>>>>>> converter. I attach these with some 2.5mm (should be 2.6mm) screws to 
>>>>>> the Model-T so its always attached.
>>>>>> https://www.sfcable.com/db9-female-to-db25-male-serial-mini-adapter.html
>>>>>> 
>>>>>> Then I put one of these adapters in between the DB9 serial port and the 
>>>>>> 9-25 adapter which creates a null modem cable.
>>>>>> https://www.sfcable.com/null-modem-adapter-db9-db25/db9-male-to-female-null-modem-mini-adapter.html
>>>>>> 
>>>>>> For my T200 I have remove pin 1 from the null modem adapter to make it 
>>>>>> happy but that's a quick fix with needle nose pliers.
>>>>>> 
>>>>>> Everybody has there preference on cable setup so eventually you will 
>>>>>> come up with a solution that works for you. Sounds like what you have is 
>>>>>> working for text transfers so that's a start.
>>>>>> 
>>>>>> Kurt
>>>>>> 
>>>>>> 
>>>>>> On Tue, Apr 9, 2019, at 5:59 PM, Thomas Morehouse wrote:
>>>>>>> Thanks Kurt.
>>>>>>> 
>>>>>>> Testing the DB9-DB25 adapter only - not the usb/serial cable - I have 
>>>>>>> continuity NOT from pin 4 of the DB9 to pin 6 of the DB25. I have 
>>>>>>> continuity from pin 4 of the DB9 to pin 20 of the DB25. That's using 
>>>>>>> the numbers printed at the pins themselves.
>>>>>>> 
>>>>>>> Should I even bother testing the others you suggest? Sounds like the 
>>>>>>> adapter already fails the test.
>>>>>>> 
>>>>>>> Tom M.
>>>>>>> 
>>>>>>> 
>>>>>>> On Tue, Apr 9, 2019 at 8:48 PM Kurt McCullum <[email protected]> wrote:
>>>>>>>> __
>>>>>>>> Ignore the USB to serial piece of the puzzle. As Brian said, it's just 
>>>>>>>> a serial port. Test the 9 to 25 adapter. One end will be female so 
>>>>>>>> it's easier to put something like the end of a paper clip into one 
>>>>>>>> hole at a time then put the probe on that.
>>>>>>>> 
>>>>>>>> Kurt
>>>>>>>> 
>>>>>>>> On Tue, Apr 9, 2019, at 5:22 PM, Thomas Morehouse wrote:
>>>>>>>>> OK - looks like I wasn't clear. In Kurt's post, he writes:
>>>>>>>>> 
>>>>>>>>> "Take one probe of the meter and put it on pin 4 of the DB9 and the 
>>>>>>>>> other on pin 6 of the DB25. It should beep or light up (however you 
>>>>>>>>> meter functions to indicate a connection). Then do the same for the 
>>>>>>>>> DSR line on pin 6 to pin 20. And finally the RTS and CTS pins 7->5 
>>>>>>>>> and 8-> 4. If they are crossed in some manner, then you will not get 
>>>>>>>>> a beep or a light."
>>>>>>>>> 
>>>>>>>>> If the usb/serial cable is a single unit (usb at one end, DB9 at the 
>>>>>>>>> other), how do I put one probe of the meter on the DB9 and the other 
>>>>>>>>> probe of the meter on the DB25? There's no DB25 on the cable, unless 
>>>>>>>>> I plug the 9-25 adapter into the DB9 - but then I can't put a probe 
>>>>>>>>> on the DB9. Jeez I feel dense.
>>>>>>>>> 
>>>>>>>>> I'm really sorry I can't follow this, but maybe I'm just overlooking 
>>>>>>>>> something really simple?
>>>>>>>>> 
>>>>>>>>> Thanks.
>>>>>>>>> Tom M.
>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> On Tue, Apr 9, 2019 at 7:56 PM Brian K. White <[email protected]> 
>>>>>>>>> wrote:
>>>>>>>>>> You don't check continuity on the usb-serial adapter. That isn't 
>>>>>>>>>> just a 
>>>>>>>>>> cable, it's really a peripheral like a disk drive or a printer, it 
>>>>>>>>>> just 
>>>>>>>>>> happens to be a peripheral that all fits entirely inside the plug 
>>>>>>>>>> housing on one end of it. There is no simple direct wire mapping 
>>>>>>>>>> between 
>>>>>>>>>> the usb pins and the serial pins. Between the usb pins and the 
>>>>>>>>>> serial 
>>>>>>>>>> pins, there is circuit board with a chip and a few other components 
>>>>>>>>>> which is converting and translatine between two entirely different 
>>>>>>>>>> kinds 
>>>>>>>>>> of signals and protocols.
>>>>>>>>>> 
>>>>>>>>>> You treat the usb-serial adapter as just a serial *port*, and ignore 
>>>>>>>>>> that it looks like a wire. Just pretend it's like a serial port 
>>>>>>>>>> built in 
>>>>>>>>>> to the back of an old desktop.
>>>>>>>>>> 
>>>>>>>>>> You check the continuity of the serial cable, which IS "just a 
>>>>>>>>>> cable". 
>>>>>>>>>> Or, really, you check the continuity of the combined serial cable 
>>>>>>>>>> with 
>>>>>>>>>> any null-modem and gender-changer adapters, and treat that all 
>>>>>>>>>> together 
>>>>>>>>>> as one "cable".
>>>>>>>>>> 
>>>>>>>>>> -- 
>>>>>>>>>> bkw
>>>>>>>>>> 
>>>>>>>>>> On 4/9/19 6:56 PM, Thomas Morehouse wrote:
>>>>>>>>>> > Thanks Kurt. I'm even denser than usual tonight I guess.
>>>>>>>>>> >
>>>>>>>>>> > From earlier posts, seems the problem (102 screen dimming) is 
>>>>>>>>>> > likely 
>>>>>>>>>> > caused by the usb/serial cable. One end of the cable is a usb 
>>>>>>>>>> > plug; 
>>>>>>>>>> > other end is the DB9.
>>>>>>>>>> >
>>>>>>>>>> > So I'm afraid I don't know how to test continuity on the cable. I 
>>>>>>>>>> > can 
>>>>>>>>>> > find pin 4 of the DB9 - but where does the DB25 fit in the picture?
>>>>>>>>>> >
>>>>>>>>>> > Or, are you saying to test the cable with the DB9/DB25 adapter 
>>>>>>>>>> > plugged 
>>>>>>>>>> > into the cable?
>>>>>>>>>> >
>>>>>>>>>> > Sorry to be the dolt again.
>>>>>>>>>> > Tom M.
>>>>>>>>>> >
>>>>>>>>>> >
>>>>>>>>>> > On Tue, Apr 9, 2019 at 10:57 AM Kurt McCullum <[email protected] 
>>>>>>>>>> > <mailto:[email protected]>> wrote:
>>>>>>>>>> >
>>>>>>>>>> > There are store bought cables that work well. Brian has done a
>>>>>>>>>> > great job putting together a list of those cables. For my machines
>>>>>>>>>> > I have a mixture of custom made cables or slim adapters. Both
>>>>>>>>>> > methods work and give me the pinout below. When you get the cable
>>>>>>>>>> > right, your M102 will be happy.
>>>>>>>>>> >
>>>>>>>>>> > But to the question at hand, don't tear apart your cable. Check
>>>>>>>>>> > it. Right now you know that pins 2,3 and 5 are all going to the
>>>>>>>>>> > right locations. You will need to check pins 4,6,7 and 8. Since
>>>>>>>>>> > those are paired lines (4/6, 7/8) one or both pairs will be 
>>>>>>>>>> > flipped.
>>>>>>>>>> >
>>>>>>>>>> > If you have a multi-meter which has a continuity check on it then
>>>>>>>>>> > you test both ends of the wire.
>>>>>>>>>> >
>>>>>>>>>> > Here is what I have found to work on all my machines and I include
>>>>>>>>>> > this in the mComm manual.
>>>>>>>>>> >
>>>>>>>>>> > 7 Wire Cable
>>>>>>>>>> > PC
>>>>>>>>>> > 
>>>>>>>>>> > Model-T
>>>>>>>>>> > DCD
>>>>>>>>>> > 1
>>>>>>>>>> > NC
>>>>>>>>>> > 
>>>>>>>>>> > 
>>>>>>>>>> > RX
>>>>>>>>>> > 2
>>>>>>>>>> > →
>>>>>>>>>> > 2
>>>>>>>>>> > TX
>>>>>>>>>> > TX
>>>>>>>>>> > 3
>>>>>>>>>> > ←
>>>>>>>>>> > 3
>>>>>>>>>> > RX
>>>>>>>>>> > DTR
>>>>>>>>>> > 4
>>>>>>>>>> > ←
>>>>>>>>>> > 6
>>>>>>>>>> > DSR
>>>>>>>>>> > GND
>>>>>>>>>> > 5
>>>>>>>>>> > ↔
>>>>>>>>>> > 7
>>>>>>>>>> > GND
>>>>>>>>>> > DSR
>>>>>>>>>> > 6
>>>>>>>>>> > ←
>>>>>>>>>> > 20
>>>>>>>>>> > DTR
>>>>>>>>>> > RTS
>>>>>>>>>> > 7
>>>>>>>>>> > →
>>>>>>>>>> > 5
>>>>>>>>>> > CTS
>>>>>>>>>> > CTS
>>>>>>>>>> > 8
>>>>>>>>>> > ←
>>>>>>>>>> > 4
>>>>>>>>>> > RTS
>>>>>>>>>> > RI
>>>>>>>>>> > 9
>>>>>>>>>> > NC
>>>>>>>>>> > 
>>>>>>>>>> > 
>>>>>>>>>> >
>>>>>>>>>> >
>>>>>>>>>> > Take one probe of the meter and put it on pin 4 of the DB9 and the
>>>>>>>>>> > other on pin 6 of the DB25. It should beep or light up (however
>>>>>>>>>> > you meter functions to indicate a connection). Then do the same
>>>>>>>>>> > for the DSR line on pin 6 to pin 20. And finally the RTS and CTS
>>>>>>>>>> > pins 7->5 and 8-> 4. If they are crossed in some manner, then you
>>>>>>>>>> > will not get a beep or a light.
>>>>>>>>>> >
>>>>>>>>>> > Hope that makes sense.
>>>>>>>>>> >
>>>>>>>>>> > Kurt
>>>>>>>>>> >
>>>>>>>>>> >
>>>>>>>>>> > On Tue, Apr 9, 2019, at 7:38 AM, Thomas Morehouse wrote:
>>>>>>>>>> >> Thanks for the comments gents. Learn something every day.
>>>>>>>>>> >>
>>>>>>>>>> >> Kurt, on the "crossed wires" issue, what is the procedure for
>>>>>>>>>> >> fixing the problem? I sure don't want to pull something apart,
>>>>>>>>>> >> or buy even *more* adapters!
>>>>>>>>>> >>
>>>>>>>>>> >> Thanks.
>>>>>>>>>> >> Tom M.
>>>>>>>>>> >>
>>>>>>>>>> >>
>>>>>>>>>> >> On Tue, Apr 9, 2019 at 10:03 AM Kurt McCullum <[email protected]
>>>>>>>>>> >> <mailto:[email protected]>> wrote:
>>>>>>>>>> >>
>>>>>>>>>> >>
>>>>>>>>>> >> What you are describing happens to me when the either the
>>>>>>>>>> >> CTS/RTS or DTR/DSR wires in your cable are crossed.
>>>>>>>>>> >>
>>>>>>>>>> >> Example. The CTS pin listens (checks for voltage) to the RTS
>>>>>>>>>> >> pin on the other end. If you have a cable where RTS goes
>>>>>>>>>> >> straight to RTS and CTS going straight to CTS, then you have
>>>>>>>>>> >> two ends of the cable both feeding voltage to the same wire.
>>>>>>>>>> >> This causes the screen to go dim. the DTR/DSR pins can
>>>>>>>>>> >> produce the same issue.
>>>>>>>>>> >>
>>>>>>>>>> >> Kurt
>>>>>>>>>> >>
>>>>>>>>>> >> On Tue, Apr 9, 2019, at 5:33 AM, Thomas Morehouse wrote:
>>>>>>>>>> >>> Now that I've got my usb/serial link working (M102 to Dell
>>>>>>>>>> >>> laptop), I notice the 102's screen get quite dim when the
>>>>>>>>>> >>> cable is in the 102's 25 pin serial port.
>>>>>>>>>> >>>
>>>>>>>>>> >>> Doesn't need to be connected to the Dell. Just when you plug
>>>>>>>>>> >>> the usb/serial cable into the 102. Unplug the cable, 102
>>>>>>>>>> >>> screen returns to normal visibility.
>>>>>>>>>> >>>
>>>>>>>>>> >>> Something to worry about? or just live with it? I wouldn't
>>>>>>>>>> >>> have thought the usb/serial cable chip would put such a
>>>>>>>>>> >>> drain on the system. Happens with battery power, or even
>>>>>>>>>> >>> with external 6 volt poweer.
>>>>>>>>>> >>>
>>>>>>>>>> >>> Thanks.
>>>>>>>>>> >>> Tom M.
>>>>>>>>>> >>>
>>>>>>>>>> >>
>>>>>>>>>> >
>>>>>>>>>> 
>>>>>>>> 
>>>>>> 
>> 

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