Ask 1000's of hams your question...
15 posts • Page 1 of 1
Please, I would like to ask to someone a question.
I have a KENWOOD TS-770E dual band all mode radio. It works quite good, but I have a problem with the display. The problem is that I can read ONLY one number of frequency. If I switch off and turn on again the power switch, I can read the following number,only that of course, and so on by turning off and on the main power switch I can read the following number.
I would like to understand the reason of this and try to repair the rtx.
Thanks a lot to anyone can halp me.
Good work and good things!
while i don't claim, to be expert of kenwood, nor do i possess one. I had gone through the service manual.
the display cycling happens due to Sa, Sb, Sc signals sent from digital unit to display unit to IC4 over there.
if you can see these signals ok, at the digital unit, yu can perhaps check for contamination on the inter conneting cable bretween the two units
It can perhaps be cleaned with isopropyle alcohal or some safer cleaning sprays with out melting out the connector plastics
if this doesn't settlethe problem, few electrolytics in the said sections can be replaced assuming that this Rig is old enough and the caps might have dried out.
Finally if the three signals are reaching the ic4 of display unit, and still it is not being decoded, ic4 (74LSD42A) can be tried to be changed.
OK dear Sarma,
I read your message,and found you've centered the problem.Really I have a problem with an interconnection cable just there between the display and the unit that drives it.It's not so tight, it disconnetcs easily and also the plug in the board is oscillating a bit. I hope that some connection failed, because if the problem is on some hard to find IC there, It would be a problem to repair it. But, in the worst case, if I won't be able to repair it, I'll try to substitute the whole freq.reader unit with a smaller, easy to find and actual unit. for now however, I'll follow your advices and I'll let you know.
So, while I'm so much grateful to you, I give my best wishes and see you as soon as possible.
I am happy to note that i could be of some help. Incidentally, there is a typo on the component name. The iC 74LS42A is a very cheap TTL chip. If specific wire or wires are loose, if were to handle, i solder them on to the pcb where the connector is soldered. the connector pins can be pushed inside using a sharp needle. if the cable is like what is used in printers or cameras , they are sold perhaps.
I do understand , replacement of module becomes a state of art of modern days. and you get fresh looks. you need not invest on such immediately.
Hallo again Sarma,
I was forgetting to tell also another thing: There is a yellow wire around the power switch that is disconnected at the moment. At this point there are about 38-40 volts and I don't know where to riconnect it.I connected it in a a hole of the power switch that goes towards the s-meter section and about 1 ampere flows.I hope to have connected it in the right place because I don't see other places to connect it(seems that it was connected right there before), but so doing I didn't notice any variations on the performance of rig. The problem of display was present of course independently of this. I don't understand what this 38 40 voltage feeds.
OK then, thanks again a lot and see you soon.
Unless we have a look at a working rig internally, we cant make out
the service document is taken as download from dk.mods and it is in black and white
Thus, unless we have an access to some color maula , or original working rig, it is difficult to comment.
Thanks a lot again, I understand that it's difficult to have an idea about this last question. However,since the yellow wire that brings the 38-40 volts is about 1,3 millimeters thick, I guess that it's for some power circuit. I'll see the schematic diagram again and try to understand the origin and the end point of this voltage.
Well, thanks very very much again and I'll tell you about my attempt of repair based on your precious advices.
My best regards and good things.
73 from IK6AIZ Ciro.
at sub module level there may not be much changes. and any available schematics or service manual could be of help.
i had the service maual from www.mods.dk
I am sorry for my English.
TS-770E have a different digital board !
If you have oscilloscope you can probe inputs of IC4 on DisplayUnit (pins 13, 14, 15) If not pulse here, probe IC18 on DigitalBoard (in 770E not IC18, but 4040 CMOS type). Pin 2 is input. If wrong pulse here, maybe SN7404 (place near of 4040) bad. My problem was in capacitor C19 and C20 (tantalum 0,15uF)
I buy here http://in.element14.com/avx/tap154m035c ... dp/1100484
15 posts • Page 1 of 1
Who is online
Users browsing this forum: No registered users and 0 guests