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TDS654C Repair

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tekkiham
Posts: 5
Joined: November 12th, 2018, 12:35 am
Country: Germany

TDS654C Repair

Post by tekkiham » November 12th, 2018, 5:46 am

Hi, that is a really wonderful forum, because before a couple of years, you wont have so much information of Tektronix Equipment.
I have an TDS654C, which doesn't boot anymore. After power-on, you see an 8. on LED. No Display, only littl flickering on the screen.
My question is: Can I use the build-in RS232 port as Debug Service port?
I think I have only to clean the Error Report for a full boot.
What about s1001? Should they be all open?

Thanks for your help.

strick
Posts: 110
Joined: March 22nd, 2016, 11:23 am
Country: United States

Re: TDS654C Repair

Post by strick » November 12th, 2018, 2:23 pm

Tekkiham,
Sorry, the normal RS-232 port is for printing only. You have to build a serial debug port. Unless you actually use your option 13 serial or parallel ports for printing, you can modify that card and plug it into the 20 flat pin header (J40 on my 784C). This allows you to get the debug results immediately after the very first part of the boot sequence, starting with the Kernel.

If the LED stops on any number or letter, something has failed and this is the only way to find out as you'll never get the normal error readout display.

look here: viewtopic.php?f=568&t=137307&p=280271&h ... rt#p280271

Strick

tekkiham
Posts: 5
Joined: November 12th, 2018, 12:35 am
Country: Germany

Re: TDS654C Repair

Post by tekkiham » November 21st, 2018, 12:40 am

Thank you Strick for the information, sorry for the late reply.
I built the adapter, tested it, but no communication. Today I found a mistake in my wiring. (A10 and B10 has to be changed in my wiring)
So I will have a short test this evening.

tekkiham
Posts: 5
Joined: November 12th, 2018, 12:35 am
Country: Germany

Re: TDS654C Repair

Post by tekkiham » December 12th, 2018, 4:56 am

Hi all,
I tried to test the communication with my option board and serial interface. But there is no reaction. Nothing to receive on power-up of the scope.
The LED Display on processor board shows ".8 " , also after 20 minutes. All lights on of the front panel , no display.
Maybe DS1486 and/or DS1250 are damaged or are blocking the running of mainprogram? Any hints?

strick
Posts: 110
Joined: March 22nd, 2016, 11:23 am
Country: United States

Re: TDS654C Repair

Post by strick » December 12th, 2018, 6:34 am

tekkiham,
do you have another TEK scope to test your debug card?

Even with a flashing .8, you should get the initial bootrom load in messages. I tested with a TDS784C and you do get messages from the debug port before the .8.

You are really hamstrung until the port is functioning.

According to the 520B component service manual, .8 is an CPU interrupt mask problem, but other things could have been flagged and you wouldn't know it.

Strick

strick
Posts: 110
Joined: March 22nd, 2016, 11:23 am
Country: United States

Re: TDS654C Repair

Post by strick » December 13th, 2018, 1:00 pm

tekkiham,
I just noticed something. I'm working on a 540C at the moment and it had a bad power supply. I changed it out and was booting the scope. It stopped on the .8. Before doing the proper look at see, I hooked up my serial debug card and guess what - it said that the Flashrom Programming Voltage is On, cannot transfer control to Flashrom. Thinking that I was going to have to reflash the board, I suddenly realized that that meant that the programming switch was in the program position.

check the position of the programming switch on the top board. The switch should be toggled to the rear position.

Strick

tekkiham
Posts: 5
Joined: November 12th, 2018, 12:35 am
Country: Germany

Re: TDS654C Repair

Post by tekkiham » December 26th, 2018, 9:48 am

Hello, merry Christmas to all of you. I just had a few Moment for Looking to the scope. I tested the TTL Oscillators Y1 and Y2.
The Y2 osc with 32 MHz is Not working. I will change it next year, because I have None in stock.

tekkiham
Posts: 5
Joined: November 12th, 2018, 12:35 am
Country: Germany

Re: TDS654C Repair

Post by tekkiham » January 14th, 2019, 10:37 pm

Hello,
so yesterday the 32 MHz TTL-oscillator arrived. I soldered it and "WoW" the scope starts up and is working fine. I tested the adapter for serial debug port at J40 and all internal Tests gave a "Passed".( only 3 connections :GND,TX,RX)
So it was a very simple error, but I wounldn't have tried it without this forum. I think it is possible to extend the input to 1 Ghz Bandwith, but I think it's not needed yet.

strick
Posts: 110
Joined: March 22nd, 2016, 11:23 am
Country: United States

Re: TDS654C Repair

Post by strick » January 18th, 2019, 2:25 pm

That's good news! If these old scopes were more popular, I'd start a symptom vs fix table. Good troubleshooting!

Strick

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