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Tek 453 Trigger Fault
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Hi everyone,
A friend of mine has contacted me (because i dabble with Scopes from time to time) about his Tek 453, its been sat in his garage for a while and is in bit of a sorry looking state but he wants to use it for some repairs on his Motorbikes. Ive only seen a photo of it so far, and he says that the fault is that the scope will Trigger on Channel B but not Channel A. He hasnt double checked it yet, but he does believe it has a 6x10cm display, so we think it might be a pre 1971 model (his photo also shows 453 not a 453A), which if TekWiki is correct, means its more likely to have Nuvistors inside. As im not familiar with the Tek scopes of this vintage or Nuvistors for that matter, im wondering if its really repairable or not, it will be a few weeks until im over his way again to get an actual look over the instrument. Just looking for some thoughts/opinions on the practicality of repairing these. Admittedly from browsing auction sites etc, it doesnt look like the 453's are all that common in the UK. Not yet browsed any service/schematics yet so may not even have any Nuvistors in the trigger circuit etc, but want to feel a bit more confident about it before agreeing to take a look at it for him. thanks in advance, Taylor |
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The 453/454 scopes are very repairable and don't let nuvistors scare you off. Think of them as transistors that get hot. They are also very reliable and easily replacable if one does go bad. Other than the nuvistors, they're all solid state (maybe some HV rectifiers, I forget if they're solid state or not). There are a few known issues. Sometimes the tunnel diodes fail - they're hard to find, but not impossible and you have to be careful with the replacement of the 2n3055 used in the HV supply. Modern ones have too much gain and may not work so if you have a bad transistor it may take a few to find one that works well. Post here if you start working on it, somebody will have suggestions.
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I've had a 453 for 25 years and never had to open it up. I did get a 454 and completely overhauled and callibrated it. I was even able to get a NOS beamfinder switch for it. I liked it so much I got a 454A to repair. Paul On Mon, Feb 14, 2022 at 02:59:02PM -0800, Taylor_d2010 wrote:
Hi everyone, --
Paul Amaranth, GCIH | Manchester MI, USA Aurora Group of Michigan, LLC | Security, Systems & Software paul@... | Unix/Linux - We don't do windows |
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The first thing you should ask your friend is what the serial number is for his 453. w140.com has the operator and service manuals- there's one set of manuals for serial numbers up to 20000, and another set of service and operator manuals for serial numbers above 20000. The low serial numbers have some nuvistors (about 5 if I remember correctly), but the nuvistors were eliminated at serial number 20000. And (2) high voltage rectifier tubes were replaced with silicon rectifiers at serial number 44359; this is described in the "20000 and up" service manual.
I agree with Paul Amaranth- the 453/454 series of scopes are nice, and they are very servicable. Only downside (to me) is their weight is a bit much compared to newer 4nn series scopes, and most of the non-A 453 and 454 scopes have only a 6x10 graticule, compared to 8x10 graticules of more recent models. Mike Dinolfo N4MWP |
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The 453 is extremely repairable. It has no proprietary ICs, for one thing. Replacement Nuvistors are surprisingly available, and even if that weren't the case, they can be replaced by JFETs without excessive drama. It's a damn fine general-purpose scope, and well worth fixing.
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--Cheers, Tom -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 2/14/2022 14:59, Taylor_d2010 wrote:
Hi everyone, |
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The manual is available at w140.com .
My low-serial-number 453 lost B trigger in 2000-something. I traced it down to tunnel diode D675. It worked after I installed a spare, then failed again. This time I traced it to Q684. I replaced it with a USSR KT3126A (PNP 20V 20mA 500MHz 2.5pF) and it has worked ever since. There are Nuvistors in the trigger circuits (V443 and V633) but they are okay. HTH, Dave Wise From: [email protected] <[email protected]> On Behalf Of Taylor_d2010 via groups.io Sent: Monday, February 14, 2022 2:59 PM To: [email protected] Subject: [TekScopes] Tek 453 Trigger Fault Hi everyone, A friend of mine has contacted me (because i dabble with Scopes from time to time) about his Tek 453, its been sat in his garage for a while and is in bit of a sorry looking state but he wants to use it for some repairs on his Motorbikes. Ive only seen a photo of it so far, and he says that the fault is that the scope will Trigger on Channel B but not Channel A. He hasnt double checked it yet, but he does believe it has a 6x10cm display, so we think it might be a pre 1971 model (his photo also shows 453 not a 453A), which if TekWiki is correct, means its more likely to have Nuvistors inside. As im not familiar with the Tek scopes of this vintage or Nuvistors for that matter, im wondering if its really repairable or not, it will be a few weeks until im over his way again to get an actual look over the instrument. Just looking for some thoughts/opinions on the practicality of repairing these. Admittedly from browsing auction sites etc, it doesnt look like the 453's are all that common in the UK. Not yet browsed any service/schematics yet so may not even have any Nuvistors in the trigger circuit etc, but want to feel a bit more confident about it before agreeing to take a look at it for him. thanks in advance, Taylor |
Mike Dinolfo
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