Tektronix 531A How fast is it and what plugins will it accept - Page 1
Forum section: electronics / testgear

author: Aperna1985
author_rank: Contributor
timestamp: January 17, 2024, 12:44:22 am
content: Hey guys I have a Textronix 531A, once I changed the plug-in that was in it, it worked perfectly. I'm working on an FM radio and I'm trying to measure the oscillator frequency which is 90 Mega Cycles. So I'm looking for a plug-in that will allow me to run at that speed. I currently have the type K plugin. Which I think is only good for 15 MHz. I see there's a 1A7 that looks very fast will my scope accept that? Or is there other good choices? I have a Tek 536 also that worked once I changed the plugin. If that is a better choice to use, I'm willing to use that.

author: PwrElectronics
author_rank: Regular Contributor
timestamp: January 17, 2024, 01:21:54 am
content: A 531A scope is rated for 15Mhz at -3dB. At 90Mhz, you may be able to see a signal but it will be reduced amplitude.I don't know what sort of AM radio you are working on but the typical consumer ones in the US would have a oscillator at 455kHz.No matter what plug in is used, you are limited by the main scope chassis.Usually there is no need to look at the oscillator directly. Lots of info on working on AM radios out there.Info on the 531 and 531A is here:https://w140.com/tekwiki/wiki/531A

author: xrunner
author_rank: Super Contributor
timestamp: January 17, 2024, 01:27:27 am
content: Quote from: Aperna1985 on January 17, 2024, 12:44:22 amWhat make and model AM radio is this?

author: Aperna1985
author_rank: Contributor
timestamp: January 17, 2024, 02:13:29 am
content: I'm sorry guys I made a mistake it's an FM radio. I normally work on Am stuff, this is my first FM I'm doing. I'm going to correct it in my post.The radio is a Channel Master 6534 AM Fm radio no have the Am portion working perfectly but Fm is completely dead. I can pass 10.7 mhz through it but can't pick up any stations it's just silent.If I could attach a PDF I'd show you guys the Schematic.

author: rvalente
author_rank: Frequent Contributor
timestamp: January 17, 2024, 11:22:02 am
content: A Textronix 531A and 90mega cycleswe are definitely talking vintage here, post some pics.You can "attach" things using the + square button bellow the message text box while posting.

author: Aperna1985
author_rank: Contributor
timestamp: January 18, 2024, 06:58:02 pm
content: I didn't see that little button to attach. Thanks.So basically there's no way to see 90MC on my Tek 531A?I attached the Schematic of the radio below.

author: David Hess
author_rank: Super Contributor
timestamp: January 18, 2024, 10:06:36 pm
content: Quote from: Aperna1985 on January 18, 2024, 06:58:02 pmThat is the short answer. The Tektronix 531A only has a 15 MHz bandwidth. Usually an RF probe to measure the envelope is more suitable.https://w140.com/tekwiki/wiki/531In theory a Tektronix 1S1 sampling plug-in can be installed to allow operation up to 1 GHz, however the chance of getting this to work with such old instruments is low so I do not recommend it, and sampling oscilloscope operation by itself even when everything works is not straightforward.https://w140.com/tekwiki/wiki/1S1

author: Aperna1985
author_rank: Contributor
timestamp: January 19, 2024, 02:15:08 pm
content: Quote from: David Hess on January 18, 2024, 10:06:36 pmWhat equipment do I need for an RF probe and can you recommend one?

author: BrokenYugo
author_rank: Super Contributor
timestamp: January 19, 2024, 03:40:32 pm
content: A basic passive RF probe is a simple diode detector circuit. Maybe biased for better picking up small signals below the diode's forward voltage. Easy to DIY, you probably have enough parts to make one.http://techlib.com/electronics/detect.htmhttps://n5ese.com/rfprobe1.htm

author: Aperna1985
author_rank: Contributor
timestamp: January 19, 2024, 09:25:28 pm
content: Oh I actually already have one. I tried it but there's literally no signal anywhere. If I use my signal generator I can pass through so I know the IF section and audio amp are working. I need to check the oscillator and I'll also need the scope for aligning the Oscillator