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Tandy 1400FD (Not HD or LT)

F

fjc618

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Mar 8, 2021
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Since I'm new here I see a lot of activity so I hope someone out there can help me out. I have this Tandy 1400FD Model 25-3501. It powers on, floppy disk drives do its seek test, keyboard lights work, and the Built in LCD monitor backlit DOES work because it lights up a kinda dark blue and its not dimming. And that's as far as I can get. No text on display, the floppy boot disk boots into dos, I know that because the floppy drive continues to read the disk as it loads. But No text on display. I checked everything all the way down to the capacitors, power supply is getting a 11.6-11.9 Volts across the board, even under load, the contrast knob doesn't have any effect. I get 2 short beeps indicating RTC battery is low, I checked that and its more clean then anything else retro I own, but I still should see text right? I cant find anything on how to fix this.
 
I wonder if the contrast knob works.

I would also check the cable from the motherboard to the monitor and see if there's a broken wire/connector.

You should certainly see text. On my 1400LT (I think they used the same display), the screen is very readable.
 
I checked the contrast knob, It all passes continuity tests, no shorts as far as i can see. I can only find service manuals for the Tandy 1400LT which has a completely different Motherboard, so it took me forever to find the traces from and to the contrast knob. I am at a loss, I don't have a external RGB monitor to use. Everything works on this FD machines except the monitor doesn't display text. Its so strange. Its a shame because this Tandy is spotless inside of it. Any other ideas, I'm all ears. Its gotta be something so simple I'm overlooking.
 
Also all wires are intact, no shorts, I tried all keyboard combinations, The scree does go off when I switch to external and internal it comes back on with just a blue screen using keyboard commands.
 
Where are you located? See if you can borrow a CGA monitor for testing. Make sure it's working first. Here's a note I found...
Code: 
The function keys at the top of the keyboard are program-specific. Their
functions depend on the program you are running. Some of these keys perform
special functions when you start the computer, such as:

CTRL  ALT  F12          LCD mode. Pressing this key combination tells the
                        computer to use the built-in LCD screen instead of
                        an external color monitor.
CTRL  ALT  F11          External color/graphic mode. Pressing this key
                        combination tells the computer to use an external
                        color monitor instead of the built-in LCD screen.
 
The capacitors in the internal power supply of the laptop are bad. That’s exactly what mine used to do until I replaced all of the capacitors (there were some nasty leakers in there too).
 
i have two 1400FD units from thrift stores in the past few years. both had leaking caps on the power supply board, nearly every electrolytic. both work fine after replacement caps. two for two with same failure.
 
Finding a external monitor is impossible for this machine. I tried those combinations, still nothing. Just a blue screen.
 
thank you, the power supply is giving a perfect 11.5-11.9 volt readings and everything seems to be getting power as it should. Funny how that effects getting text on the display. Looks like I have power supply repairing to do. After I get my workstation built, I will definitely get it fixed.
 
Funny how the power supply effects getting text on display even though everything is getting near perfect voltage readings. Looks like Ive got some work to do lol. thank you for the response.
 
Sorry been busy as heck. Turns out it is the power supply. I wish I can just buy a new one. Every Capacitor needs to be replaced. Its so funny how it gets almost perfect voltage.
 
Sorry for the late reply, been very busy. I tore down the power supply, every capacitor needs to be replaced. I wish I can buy a new power supply. Is there any place I can order one that works? Replacing these won't be easy for me, for some folks its a cake walk. haha.
 
You may be able to find someone to repair it for you. Buying another won’t do any good because it will have the same issue unless it’s already been fixed.
 
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