E-design
Advanced Member level 5
tek scopes
There are a lot of the Tek 400/2000 series scopes available on ebay these days. These scopes are good value for money if still in good working order. I must have fixed and calibrated well over a hundred scopes of all makes in my lifetime from business to helping out friends and my hobby(collecting/fixing old test equipment).
Things to watch out for on TEK:
Never attempt any repair without the service manual, unless you know the scope very well!
Never tweak pots to try and fix a fault. It may be difficult to get the adjustments correct again after fixing the real fault.
First check all the supplies for correct voltages and excess ripple.
Ripple because of dried up capacitors can cause some weird problems.
Make sure the voltage selector bar is plugged in for the correct range. You have a choice Hi or Lo range. Sometimes this may cause regulation problems. Make sure on the 465, 475's that the low line indicator above the power switch is not lit up.
If you get a unit that needs some specialized part like custom IC, tube, switch etc. you will be stuck unless you have another unit to strip parts from.
Triggering problems on 400 series maybe due to faulty tunnel-diodes, and you will need the exact replacement. Very difficult to get unless you have a scrap unit.
Sweep problems on various speeds, may be as simple as replacing a single cap or resistor, but is often due to the sweep selector switch starting to fail or becoming intermittent. These switches are very complicated. They can, and I have repaired them in the past, but it is not a easy job.
Problems on the vertical attenuator is often due to dirty contacts on the selector or faulty or intermittent plug in attenuators blocks.
Oscillation in a channel when set to the most sensitive setting may be due to someone being lazy and leaving off some screen covers on the attenuator assy during a earlier repair attempt.
Another common problem is no beam due to a faulty HV block. Again you need a used part or if you know what you are doing, it can be replaced with a TV tripler. I got many 400 Tek scopes back to life by fitting triplers.
Focusing problems are often caused by resistors going high in value, or faulty HV capacitors and diodes in the HV section.
The fan controller IC can be replaced by discrete transistors.
Some faults make people believe that the CRT is faulty, because they can't get any beam on the screen. Here is a trick I use. First verify that the CRT heater is working by looking from the back of the tube. Next turn up the intensity to max. Then in a somewhat darkened room turn the scope off and on a few times while watching the screen. If you see any sign of trace flash on the screen, chance is good that the CRT and EHT is OK. The lack of beam may be caused by control-grid or deflection problems. I have replaced very few faulty scope CRT's in the past. The EHT can be measured with a EHT probe for checking and adjusting.
The 465, 475/A are fairly easy to fix if you have a reasonable background in theory and some troubleshooting experience. The 468 is not bad unless you get a fault in the digital storage section. Many custom IC's in there. The 485 is a small very high performance scope BUT NOT VERY EASY TO FIX. I love them (have 2 myself) but always hate fixing these. Part of the problem is getting at things.
If you are having trouble with a specific section, it pays to read the theory and circuit description in the manual.
Fixing the TEK 2000 series is not bad, with the exception of the 2465. This is not easy to fix due to the use custom wideband modules. Combine this with the integrated digital control and readout, and you will have a job on your hand. My advice is NOT to buy one on ebay to use unless it is in guaranteed perfect working order. Even a small problem may prove impossible to fix due to lack of spares.
The 2000 series have switching supplies that can fail, resulting in a dead unit symptom. Fixing the switching supply is often all that is wrong with the scope.
E
Here is some words of wisdom I found from a seller on ebay (maybe worked/working for Tek on scopes) Basically agreeing with my comments on the 2400 scopes.
"2400s are all I work on, so mine shall arrive working correctly. Keep that in mind when you gloss over others you might find elsewhere, albeit for less, described perhaps as "worked ok last time" (meaning not any more) or "pulled from a working environment" (because it quit working) or "lit up ok, but don't know how to test" (test would fail). If you buy theirs and you find a problem, my standard $600 flat repair fee will evaporate your "savings". It should be obvious that sellers with "scrap, pawn, or surplus,..." as part of their name cannot be expected to deliver what I can."
There are a lot of the Tek 400/2000 series scopes available on ebay these days. These scopes are good value for money if still in good working order. I must have fixed and calibrated well over a hundred scopes of all makes in my lifetime from business to helping out friends and my hobby(collecting/fixing old test equipment).
Things to watch out for on TEK:
Never attempt any repair without the service manual, unless you know the scope very well!
Never tweak pots to try and fix a fault. It may be difficult to get the adjustments correct again after fixing the real fault.
First check all the supplies for correct voltages and excess ripple.
Ripple because of dried up capacitors can cause some weird problems.
Make sure the voltage selector bar is plugged in for the correct range. You have a choice Hi or Lo range. Sometimes this may cause regulation problems. Make sure on the 465, 475's that the low line indicator above the power switch is not lit up.
If you get a unit that needs some specialized part like custom IC, tube, switch etc. you will be stuck unless you have another unit to strip parts from.
Triggering problems on 400 series maybe due to faulty tunnel-diodes, and you will need the exact replacement. Very difficult to get unless you have a scrap unit.
Sweep problems on various speeds, may be as simple as replacing a single cap or resistor, but is often due to the sweep selector switch starting to fail or becoming intermittent. These switches are very complicated. They can, and I have repaired them in the past, but it is not a easy job.
Problems on the vertical attenuator is often due to dirty contacts on the selector or faulty or intermittent plug in attenuators blocks.
Oscillation in a channel when set to the most sensitive setting may be due to someone being lazy and leaving off some screen covers on the attenuator assy during a earlier repair attempt.
Another common problem is no beam due to a faulty HV block. Again you need a used part or if you know what you are doing, it can be replaced with a TV tripler. I got many 400 Tek scopes back to life by fitting triplers.
Focusing problems are often caused by resistors going high in value, or faulty HV capacitors and diodes in the HV section.
The fan controller IC can be replaced by discrete transistors.
Some faults make people believe that the CRT is faulty, because they can't get any beam on the screen. Here is a trick I use. First verify that the CRT heater is working by looking from the back of the tube. Next turn up the intensity to max. Then in a somewhat darkened room turn the scope off and on a few times while watching the screen. If you see any sign of trace flash on the screen, chance is good that the CRT and EHT is OK. The lack of beam may be caused by control-grid or deflection problems. I have replaced very few faulty scope CRT's in the past. The EHT can be measured with a EHT probe for checking and adjusting.
The 465, 475/A are fairly easy to fix if you have a reasonable background in theory and some troubleshooting experience. The 468 is not bad unless you get a fault in the digital storage section. Many custom IC's in there. The 485 is a small very high performance scope BUT NOT VERY EASY TO FIX. I love them (have 2 myself) but always hate fixing these. Part of the problem is getting at things.
If you are having trouble with a specific section, it pays to read the theory and circuit description in the manual.
Fixing the TEK 2000 series is not bad, with the exception of the 2465. This is not easy to fix due to the use custom wideband modules. Combine this with the integrated digital control and readout, and you will have a job on your hand. My advice is NOT to buy one on ebay to use unless it is in guaranteed perfect working order. Even a small problem may prove impossible to fix due to lack of spares.
The 2000 series have switching supplies that can fail, resulting in a dead unit symptom. Fixing the switching supply is often all that is wrong with the scope.
E
Here is some words of wisdom I found from a seller on ebay (maybe worked/working for Tek on scopes) Basically agreeing with my comments on the 2400 scopes.
"2400s are all I work on, so mine shall arrive working correctly. Keep that in mind when you gloss over others you might find elsewhere, albeit for less, described perhaps as "worked ok last time" (meaning not any more) or "pulled from a working environment" (because it quit working) or "lit up ok, but don't know how to test" (test would fail). If you buy theirs and you find a problem, my standard $600 flat repair fee will evaporate your "savings". It should be obvious that sellers with "scrap, pawn, or surplus,..." as part of their name cannot be expected to deliver what I can."
