On Sun, 20 Jan 2013 11:17:05 -0500, "tm"
wrote:


"John Fields" wrote in message
.. .
On Sat, 19 Jan 2013 18:59:59 -0500, "tm"
wrote:


"John Fields" wrote in message
...
On Fri, 18 Jan 2013 16:36:30 -0500, "tm"
wrote:


"John Fields" wrote in message
om...
Hello,

I have a Tektronix 465 which is perfect in every way except that the
horizontal trigger has gone belly up and the trace free-runs no matter
what.

Clue, please?

Thanks,

--
JF


Bad tunnel diode?

Do you have the service manual?

http://bama.edebris.com/manuals/tek/465(2)/

---
Yes
---

Can you trigger the B sweep?

---
Yes.

--
JF

The TDs are Ge and heat will kill them. Use forceps against the body to
solder them. Do you have access to a curve tracer? If so, check the TDs
for
the A sweep. I usually check them in circuit. I think they are 4.5 ma or
10
ma diodes.

---
OK
---

Feed in a test waveform to the external trigger input and see if the
trigger
view works.

---
It does.
---

You do have it in norm mode vs auto, right?

---
In AUTO it free runs, no matter what, and in NORM it does nothing, no
matter what.
---

Can you line trigger?

---
No.

--
JF

The transistors and ICs are all in sockets and on the Trigger board that
faces to the right. While it is a good bet that the "Fire" TD has failed, it
may be worth your time to open the scope up and poke around those parts.
U-870, and the transistors around that area. There are many waveforms given
in the manual and with another scope they can save much time. Luckily it's
all out in the open.

While it is open, you might verify all the power supply voltages and ripple
levels per the manual. In fact, do that first.

Good luck, the 465 is a fine instrument.

---
Yup.

I bought this one, (S/N B011240) used, about 20 years ago, and this is
the first trouble it's given me.

I also have a 2215A, a T922, a 2465A, and an HP54602; all working and
all beauties. :-)
---

Regards,
tm

---
Thanks for the help, it's appreciated.

--
JF