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Re: 465B - Question regarding C4331 / CR4405
tom jobe
Dipped tantalums failing in a complete short without exploding is very ordinary in that vintage of gear.
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On 5/30/2018 7:05 AM, n4buq wrote:
I thought tantalums were noted for spectacular failure events. If this is indeed my shorted component, it simply failed quietly which I didn't expect. I'll have to lift one side to see if that's the problem (but do suspect it is). |
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Re: 465B - Question regarding C4331 / CR4405
I thought tantalums were noted for spectacular failure events. If this is indeed my shorted component, it simply failed quietly which I didn't expect. I'll have to lift one side to see if that's the problem (but do suspect it is).
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The odd thing is this failure mode was intermittent for a quite a while with failure events lasting a second or so in between long periods of symptom-free performance. I just didn't think tantalums failed that way but maybe so. Thanks, Barry - N4BUQ ----- Original Message -----
From: "Harvey White" <madyn@...> |
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Re: 465B - Question regarding C4331 / CR4405
I thought I recalled them being listed as electrolytics but wasn't sure.
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "tom jobe" <tomjobe@...> |
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Re: 465B - Question regarding C4331 / CR4405
On Wed, 30 May 2018 09:29:11 -0400 (EDT), you wrote:
Checking a few things in/around the LVPS of my 465B and noticed that TP4339 checks shorted to ground. I presume that's most likely C4331 or CR4405. Looking at the board, C4331 appears to be a rather large(ish) bulb-like device which I took to be a tantalum; however, the parts list shows that as a 47uF electrolytic. The colors tend to agree with those numbers (e.g. yellow dome, violet middle, etc.) but is that indeed an electrolytic or tantalum?I'd go for a dipped tantalum. They're known to fail. Harvey
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Re: 465B - Question regarding C4331 / CR4405
tom jobe
The parts lisitings call tantalum capacitors electrolytics.
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That is just a normal dipped looking tantalum capacitor. Most will suggest that you replace it with the highest voltage tantalum you can find. On 5/30/2018 6:29 AM, n4buq wrote:
Checking a few things in/around the LVPS of my 465B and noticed that TP4339 checks shorted to ground. I presume that's most likely C4331 or CR4405. Looking at the board, C4331 appears to be a rather large(ish) bulb-like device which I took to be a tantalum; however, the parts list shows that as a 47uF electrolytic. The colors tend to agree with those numbers (e.g. yellow dome, violet middle, etc.) but is that indeed an electrolytic or tantalum? |
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Re: 465B - Question regarding C4331 / CR4405
Oh, and, I mention CR4405 as I suppose it's possible that's shorted instead of C4331.
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Thanks, Barry - N4BUQ ----- Original Message -----
From: "n4buq" <n4buq@...> |
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465B - Question regarding C4331 / CR4405
Checking a few things in/around the LVPS of my 465B and noticed that TP4339 checks shorted to ground. I presume that's most likely C4331 or CR4405. Looking at the board, C4331 appears to be a rather large(ish) bulb-like device which I took to be a tantalum; however, the parts list shows that as a 47uF electrolytic. The colors tend to agree with those numbers (e.g. yellow dome, violet middle, etc.) but is that indeed an electrolytic or tantalum?
I can share a picture but this cap hangs out right next to TP4339 (+15V test point). Anyone know? Thanks, Barry - N4BUQ |
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Re: Seeking 485 scopes
It would help if you would mention the continent!
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It is probably irrelevant to you, but I had a faulty U660. One internal resistor between pins 1/12 or 6/7 went open circuit. I "replaced" it by soldering an SMD equivalent in parallel, positioned between two nearby convenient components. I'm afraid I don't remember the value; I measured the other resistor. The net result was that the risetime was 1.25ns (not 1ns) and there was a slight "hesitation" in the waveform at 90% of amplitude. On 30/05/18 06:36, Reed Dickinson wrote:
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Seeking 485 scopes
Greetings Forum Members:
I would like to buy any 485 scopes that are surplus to your needs, operable or inoperable. I have no restrictions on condition other than they not be stripped of all useful parts. I am especially interested in Tek P/N 155-0064, the U660 vertical output LSI IC used in the 485. Please describe what you have, quantity and price in your first communication. Shipping would be my responsibility. Please contact me off forum. Reed Dickinson reed714@... |
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Re: Audio Anateur Magazine Back Issues
I think this was aimed mostly at me. Sorry for stirring up the pot.
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On 5/29/2018 8:09 PM, Ed Breya via Groups.Io wrote:
Dennis said: --
Richard Knoppow dickburk@... WB6KBL |
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Re: Audio Anateur Magazine Back Issues
I am sorry I wasn't more clear. My request is way OFF TOPIC which is why I
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asked anyone to please respond OFF LIST. Thank You Dennis Tillman W7PF -----Original Message----- -- Dennis Tillman W7PF TekScopes Moderator |
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Re: Audio Anateur Magazine Back Issues
Sigh!
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I did say OFF LIST in my post for a reason. This is way off topic. Dennis Tillman W7PF -----Original Message----- -- Dennis Tillman W7PF TekScopes Moderator |
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Re: Audio Anateur Magazine Back Issues
I always forget something. There is a good deal on all of these amplifiers in the famous "Radiotron Designer's Handbook" 4th edition (the big red one) available on line from tubebooks.org and a couple of other places. I've been able to find a couple of decent copies used via Amazon and prefer actual books to the electronic variety.
-- Richard Knoppow dickburk@... WB6KBL |
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Re: Audio Anateur Magazine Back Issues
Doesn't work any better, sorry. You must copy and past the URL for it to work.
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Williamson talks about the transformer. A transformer was made to his specifications by Partridge and sold in the U.S. as well as the U.K. These were reportedly thoroughly superior to standard commercial transformers even of the best quality. Later Keros and Haffler made transformers under the Acrosound name with similar superior quality. Frank McIntosh also made a patented type of transformer with superior quality for his amplifiers but they were never sold separately. The original Williamson circuit did have problems with parasitic oscillations which was cured with relatively simple changes in the circuit. My own experience back when I could hear very well, was that McIntosh amps sounded better than most Ultra-Linear amps. I don't know if I ever had a genuine Williamson. The general quality of amplifiers at the time Williamson came out with his was pretty awful. The Leak Point One and Acoustical QUAD were revelations to those used to the usual public address stuff. I am now hors de combat due to my hearing loss. On 5/29/2018 6:51 PM, Richard Knoppow wrote:
??? The mail truncated the URL try --
Richard Knoppow dickburk@... WB6KBL |
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Re: Audio Anateur Magazine Back Issues
The mail truncated the URL try
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< perlatives.pdf> On 5/29/2018 6:05 PM, Ted Rook wrote:
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Richard Knoppow dickburk@... WB6KBL |
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Re: Audio Anateur Magazine Back Issues
Those with an interest in the gruesome details of tube amplifier design may enjoy this article
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published by Williamson in Wireless World in 1952 following some exchange of opinions between UK and US hifi amplifier makers perlatives.pdf My first hifi amplifier was a Quad tube set. It is long gone. Ted On 29 May 2018 at 16:52, Richard Knoppow wrote:
Williamson was famous for his driver circuit. His original amplifier used triodes or triode connected pentodes. The circuit was modified a few years later to improve its stability and get rid of some spurious oscillations. When the Ultra-Linear output circuit came out the amp was again modified to take advantage of it and I think this is what you are thinking of. Dyna published an article by David Haffler on how to make the conversion and Dyna or maybe it was Acrosound, made a suitable transformer. Look through the material on Tubebooks.org and also magazines on American Radio History. Sometime around the mid 1950s the increased dynamic range of recordings made increased power advantageous. The low efficiency speakers that began to come out after stereo was introduced made further power increase desirable. Charts from the 1940s for motion picture theater sound show that power on the order of 10 to 20 watts was considered sufficient for theaters of 500 to 1000 seats! Efficient speakers and limited dynamic range was the reason along with the high cost of amplifier power. By the mid 1960s 10 watts was considered a toy and home amplifiers of 50 watts were commmon. It does make a difference if the amps are of good quality. The conversion of an early Williamson amp to an Ultra-Linear output just about doubled its output power. On 5/29/2018 1:24 PM, r221b@... wrote: If I recall correctly, the old HH Scott LK-72 amplifier was 40 watts (per channel) and used the Williamson output circuit. Maybe that can help you? Don't have the AA magazines though. Rich-- Richard Knoppow dickburk@... WB6KBL |
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Re: Audio Anateur Magazine Back Issues
Williamson was famous for his driver circuit. His original amplifier used triodes or triode connected pentodes. The circuit was modified a few years later to improve its stability and get rid of some spurious oscillations. When the Ultra-Linear output circuit came out the amp was again modified to take advantage of it and I think this is what you are thinking of. Dyna published an article by David Haffler on how to make the conversion and Dyna or maybe it was Acrosound, made a suitable transformer.
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Look through the material on Tubebooks.org and also magazines on American Radio History. Sometime around the mid 1950s the increased dynamic range of recordings made increased power advantageous. The low efficiency speakers that began to come out after stereo was introduced made further power increase desirable. Charts from the 1940s for motion picture theater sound show that power on the order of 10 to 20 watts was considered sufficient for theaters of 500 to 1000 seats! Efficient speakers and limited dynamic range was the reason along with the high cost of amplifier power. By the mid 1960s 10 watts was considered a toy and home amplifiers of 50 watts were commmon. It does make a difference if the amps are of good quality. The conversion of an early Williamson amp to an Ultra-Linear output just about doubled its output power. On 5/29/2018 1:24 PM, r221b@... wrote:
If I recall correctly, the old HH Scott LK-72 amplifier was 40 watts (per channel) and used the Williamson output circuit. Maybe that can help you? Don't have the AA magazines though. Rich --
Richard Knoppow dickburk@... WB6KBL |
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Re: Audio Anateur Magazine Back Issues
If I recall correctly, the old HH Scott LK-72 amplifier was 40 watts (per channel) and used the Williamson output circuit. Maybe that can help you? Don't have the AA magazines though. Rich
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---------- Original Message ----------
From: "Dennis Tillman W7PF" <dennis@...> To: <[email protected]> Subject: [TekScopes] Audio Anateur Magazine Back Issues Date: Tue, 29 May 2018 11:37:40 -0700 Does anyone have access to back issues of Audio Amateur magazine? I'm looking for the following articles 1979 Williamson's 40W power amplifier 1990 A simple Curve Tracer (Part 1). I have part 2. 1991 Back to the future with Williamson and Watling Contact me off list at dennis@... <mailto:dennis@...> . Thanks, Dennis Tillman W7PF ____________________________________________________________ We Say Goodbye To Lara Spencer risingstarnewspaper.com |
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Re: New to me Tek 2465A DM - Not Getting Waves
Here is the 2465a battery replacement pics, I was thinking b series I guess. Same as the 2430 before the a. sorry for the mixup. So far so good on the 2430a it still percolating along and doing fine. I would try a good battery before the recal route, you may have enough old battery to retain the settings. My 2430 did with the new coin cell temporary I was able to get the data from the old chip, all I got on the screen was jibberish with the almost dead cell. It was like 1.2v and giving errors before I got the new chips it was totally unusable as far as a scope. Good luck and I hope you get them all up and running. Sent from Mail for Windows 10 From: Chuck Harris Sent: Tuesday, May 29, 2018 1:41 PM To: [email protected] Subject: Re: [TekScopes] New to me Tek 2465A DM - Not Getting Waves 2465A scopes don't have a Dallas NVRAM at all. They use a low power CMOS RAM chip, and a lithium cell battery with all of the associated power control circuitry. If you want to retain your calibration constants, you must connect about 3V worth of battery power to the diode that is in series with the + terminal of the lithium cell, to ground before unsoldering the old cell, and maintain the power until you have soldered the new cell in place. -Chuck Harris Alan Halls wrote: Thank you Dewey and John. I started going through the PDF you linked and my |
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