I have a 4-channel Tektronix 2445A I bought sometime around 2008(?) Basically, this scope is almost a 30-year old equipment, circa 1987 based on my research. I like this 2400 series scope compared to the Tek 2000 series it replaced, the 2445A being a 4 channel scope and having the ability to easily measure Delta-V and Delta-T (voltage and time/frequency using movable currors).
There are many variants of the Tektronix 2445 scope. There is the plain 2445, a 2445A, and a 2445B. There are other scopes that look similar, like the 2465A, which looks exactly like a 2445A. It’s very confusing sometimes when downloading Service Manuals so make sure the Service Manual you have is specifically for your equipment. There may be slight variations in schematics, or board layout/parts placement.
I noticed problems with my Tek scope when attempting to do voltage measurements using Channel 1. The results I’m getting were not making sense (i.e. scope reading was larger than the actual voltage I’m feeding into it’s BNC jack!) Switching the probe to Channel 2 showed the correct readings, so I know the problem is specific to Channel 1.
At this point, I’m debating between buying another replacement scope from eBay to replace this 2445A, buying a brand new (and spending more) on new scope, or attempting to fix this 2445A.
If I buy another *used* scope from eBay, it will be another gamble since I will not know beforehand the actual and true condition of this equipment.
Buying a *new* unit will cost more than $1000 dollars, for a name-brand 2-channel unit.
And trying to fix this scope, I’ll be without a working scope during the time this scope is disassembled. Plus… how can I fix a scope, if I don’t have another scope to use to probe things around?
In the end, I found a good deal on a brand new Rigol DS1054Z digital oscilloscope. This DSO is fully featured, 4 channels, and best of all costs only $399. A discount code further lowered it to $375 with free shipping… + a free $15 gift card. Did I say it’s fully loaded with features? Though some of the features are only on Time Trial… but fear not, a “hack” can be found on the Internet and just by entering a few hex numbers, you can “upgrade” this scope to a 100Mhz, fully-loaded with all the bells and whistles options.
The nice thing about this scope are the “statistics” about the waveform you’re viewing. Plus, it’s a storage oscilloscope so you can capture events and review them later in more detail. But this post is not about the Rigol scope. This post is about my Tektronix 2445A and my desire to repair it, restore it and bring it back to a fully working condition.
The Service Manual
The first thing you should do before attempting to repair/restore/calibrate your test equipment is find it’s service manual. Do not attempt to repair complex test equipment like scopes, signal generators, etc. without a service manual, as it will be almost impossible to know what you’re doing. There are several trimmers and test points on the board, and you won’t know just by casual observation of the board which is which.
Google is your friend here, but beware because Google may bring you results that are not exactly for the equipment model/batch/variant you have. A 2445 scope is not the same as a 2445A scope, and a 2445A scope is not the same as a 2445B scope. Yes, some functionalities, schematics, parts, boards may be shared between these different scopes, but it’s better if you get the exact Service Manual for your equipment.
Another issue I encountered is some of the PDF Service Manuals you may download are just “image scan” of the original manual. Therefore, finding specific “text” or “keywords” in this PDF manual is impossible… and this can become a hassle as you’re forced to read the entire manual, or at least go through all the pages and get yourself become familiarized with it.
There are companies out there that sell OCR’d (Optical Character Recognition) scans of the PDF manuals. This makes the PDF searchable for keywords, which is a very useful feature! The downside is you have to pay for these kind of PDF Service Manuals. The good news is it doesn’t cost much… $15 typically. It’s well worth the money given the ability to do full text search on these PDF Service Manuals!
On the next post, I’ll show the guts of the Tektronix 2445A scope.