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Thank you for your reply Ozan, I found one old Tektronix Reference document about the min and max loads that I have uploaded to the files section (

I recently got a 453 that needed some work that I got going good but it’s missing the rear cover plate. It’s the early version that takes the separate power cord. If anyone has a parts unit with a

======== Hi Roger, What I meant is if the +130V measures within target, while loaded in the mainframe , then no need to touch it. First PSU needs a minimum total load so that switcher section works in

Thank you for your reply Ozan, But I still don't understand why there is a minimum load requirement for the +130 rail, as suggested by Morris. According to your explanation, if it measures ok, I think

==== +130V is the main voltage switcher regulates, all other pre-LV regulator voltages (+7V, +54V, etc.) depend on +130V being correct. ?It is sensed at the top of R1292 and adjusting R1293 to set

Thank you all for the reply. Would you plase explain why there is need to add a load to the +130V rail? I followed the schematics and it seems there is no regulation/feedback for it, so why a load is

=== Hi Roger, I looked at the schematic of Dennis Tillman load. It is for a different model and missing the load on 130V line. Minimum load currents you need on 7904 (from H?kan): -50 V: 0.08 A -15

Rogerio O ( /g/TekScopes2/topic/tek_7904_heps_operation_with/105875301 ) 02:34 #16878 ( /g/TekScopes2/message/16878 ) When I made my dummy load for the 7904 I used

I tested my dummy load after disconnecting the HV section and the HEPS went to ticking mode. However, it worked when connected to the scope. I think I have double checked all the connections, but I

==== Your suggestion would work, as an alternative pins 2&6 of P1417 should be same ground as pin 10 of P1482 (you could confirm with a DVM). Load could be between pins 2&6 and pin 3&4. You need 0.3A

It is fairly typical of the beast, but any mesh/quadrapole lens fast scope is fuzzier than, say a 547, because the beam granularity is magnified over that of a classic CRT. The thing that most don't

Thnak you all for the replies. I am lost about where to connect the load to the +5Vlamp rail. As far as I can make sense of the schematics the pin 10 of P1482 is connected to ground. According to

Chuck: Never had an issue on my 7904 for sharpness vs 7104, 2465B etc. Ozan: See alo the EEV blog on this subject and the many dummy loads for TEK scope PSU Jon

== Hi Roger, Could you clarify your question about lights common? +5VL is one of the supplies monitored by the switcher, it needs some load. You can tap lights connections at P1417 (violet colored

One thing I should mention is the 7904 on its best day has a very blurry trace. It is not as sharp as, say, a 547, or 545B. It is not as sharp as a 2465, either. The reason it is inherently blurry is

Thank you for your reply Ozan. I have measure the resistance to ground on the power rails at Z-axis boards and they were similar to the ones described on the famous article from Servicescope. From

== On 7904 LV regulator there are resistors connecting outputs to their sense inputs in case motherboard doesn't provide sense return. For example R1429 is such a resistor for +50V supply. For

Hi folks, I decided to create a new thread with with question so other (as inexperienced as I am) may benefit from the answers. While trying to find why my 7904 was showing a blurry trace, I heard a

I had one (in a piece of non-Tek gear) get red hot and glow so brightly that for an instant I thought it was a LED! Fortunately there was no collateral damage.

Hello everyone, I am selling my trusty TM503. It’s the first generation, very early 1970s, and I have modified it with the IEC line input module and it has had all 3 caps replaced with brand new