On Fri, 29 Jun 2018 16:12:16 -0500, you wrote:
Thanks for the nudge Harvey. And for the helpful suggestions from other
scope ninjas here. I have some breadboards and lots of passive
components...even a few transistors.
Many years ago, I was playing with transistors when they (almost)
first came out. It's a learning process.
Maybe if the smoke clears for awhile
I will buckle down and join the modern world. I have always enjoyed old
technologies, arts, crafts and maybe that comes with over 7 decades and
many very different careers and hobbies.
I've got electronics that are old, but I've decided to concentrate on
mostly the solid state stuff for test equipment. It has more to do
with the availablity of the tubes and the capability of the
equipment.... (let alone the amount of heat that a Tektronix 513D
generates, had one, know that).
Get too far back and you get tubes and difficult to find transistors,
get too far forward, and you get CPLD's and FPGA's and custom ASICS.
All of which mean that finding a part is difficult, if not impossible
to replace once you have the part. Otherwise, it's replacing the
board.
Electronics is a good fit for my
beat up old body, because it challenges me mentally and I can do it
sitting.
Programming can be fun, too. You have to like to do it, though.
Plus to see a young musician fix or build their own tube amp is
really rewarding. But most old tube circuits and the ones we build are a
corncob compared to a wheat field re to this scope....and IT is 40 year old
technology. I hope my new tds460a outlasts me, because just one bad chip
is probably beyond what I can hope to fix in Mexico. But I'm already
looking at hot air soldering gear....just in case.
Hot air soldering/desoldering is not all that bad. If you can find a
good pace or metcal system at a reasonable price, I'd go for it. I
prefer Metcal, but you have to consider the ease of getting tips for
it.
In the mean time I am a grateful student here among so many willing
teachers. I am already way ahead in understanding compared to where I was
when opened the 465 case just a few days ago. Thanks to everyone who has
shared their ideas and instruction. It almost makes me want to buy a few
more of these bargain "as is" 465, 475 series scopes. Hearing that fan
come on today and seeing at least something on the display was indeed a
great early birthday present. ?
Good. Glad to hear it, and eventually, repairing these can be fun, but
it's also fun to actually use the equipment.
Harvey
On Friday, June 29, 2018, Harvey White <madyn@...> wrote:
On Thu, 28 Jun 2018 19:57:26 -0700, you wrote:
I'm so sorry that I havent kept up with all of the help here, Albert. I
wasn't expecting such a willingly helpful group when i joined the group.
This has been an exceptionally busy June for me. I'm recovering from
recent heart surgery and seem to be falling behind on my lab repair work
among other things. But i did get a bit of time [about 30 min] to follow
up on some of the suggestions here. The access board layout diagram is
pretty hard to read and not all that much is labeled on the actual board so
it is going slower for someone used to point to point and turret board
electronics. I have almost zip experience with transistors or pcb layout.
But I'm determined to get this figured out.
You might, for the sake of general learning, get some breadboard kits,
general purpose transistors, and start breadboarding some transistor
amplifiers and switches. It would give you a feel for the parts.
For PCB layout, consider that you are doing the same as wiring a
breadboard (the type with millions of holes). The rules, though, is
that the traces cannot cross each other on the same side (otherwise
they're the same trace). They must go from layer to layer through a
plated through hole called a via. On dual layer boards, you have
simply a top and bottom, and the vias go all the way through. On 4
layer boards, there's a top, bottom, and two inner layers. Frequently,
some of the layers are reserved for power and ground.
So PC boards are not all that bad.
One question: did you mean c1549 and cr1549? You were mentioning the
15v rail and c1559 and cr 1559 are on the 5v rail.
Re the video, it was the model and post sn 250000 that caught my eye an
invoked my comment. Misery likes company and to see someome trying to fix a
no screen problem gave me a bit of hope. There is not much other video
tutorial that I could find, good or bad, re what i have a problem with. I
am completely self taught in electronics and despite recognizing the less
than stellar technique, I actually learned a little about layout even if
nothing else was up to par judging from the comments.
I knew almost nothing about this 465 before I started this thread and I'm
gaining ground. Poco a poco andamos lejos.
You might want to look at linear supplies and how they work. The
principles between a linear regulator for tubes and transistors are
identical, but the different parts will give you different voltages on
the transistors (vs the tubes). Depletion mode N channel FETS are
most like tubes, once you get to that point. (triodes, thank you).
As in any such project, suspect the power first, then look at
functional blocks. I've had 468's with high voltage resistor network
problems, which will throw off the high voltage. There's a high
voltage divider network that's part of the feedback from the high
voltage output back to the regulator.
Harvey
Thanks again to all for the patience and wealth of info. I have a
birthday on Saturday. Maybe i will have time to spend a few more hours
figuring this out. Seeing a trace on the screen would be way better than
candles. ?
