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Re: 7704A - MOD3089

 

Make that a 2k that I placed across R3468. That makes it pretty close to 953-ohms. I need to stop relying on my memory...

Barry - N4BUQ

Can someone please tell me where I can find the details regarding MOD3089 for a
7704A? I was perusing one of the PDF scans of the service manual and notice
there are several mods that seem to relate to the Guernsey versions of this
scope, one of which is MOD3089 which changes R3468 to a 953-ohm resistor.

I have had problems getting the vertical positioning as close to correct as I
can and one of the ways I did that was to place a 1k across R3468 (a 1.8k)
which has helped that a bit. It makes the character height a bit smaller which
keeps them both from being at the very top of the two graticule lines so I
would be interested in knowing the details of that mod.

Thanks,
Barry - N4BUQ
Tektronix TDS744A CRT caps parts numbers

 

Greetings to all members of the group. Well, I'm not an expert in electronics; I would say I'm a humble enthusiast. That's why I come to you to request your help. A few years ago, I bought a TDS744A with serial number B040296, and when I turned it on, the monochrome CRT showed no image. I connected the oscilloscope to a monitor through the VGA output, and it displayed an image without any issues. A couple of months later, I turned it on again, and it didn't power up. The LEDs on the panel only flickered. These days, I disassembled it and found that the RIFA capacitors of 1n in the power supply were damaged. I replaced them with PME271Y422MR30, but I still have not turned on the oscilloscope.
Taking advantage of having the device disassembled, I checked the capacitors on the CRT board and found several undervalued and some shorted. Could someone please provide me with the list of capacitor parts for this board to replace them? It will be of great help as I don't want to use just any capacitor. I know the device would work with general-purpose capacitors, but I think it would be better to use the appropriate ones.
By the way, I know that a great engineer designed a load to test this PSU. Could someone please sell me, if someone have it, the PCB to assemble the load? I will be very grateful for your help.
P.S.: I was a radio amateur some years ago, and my old QSL was OA4DMA.
With gratitude.
Rafael Suarez
Re: Need/want a bench top DC power supply.

 

On Sun, 17 Dec 2023, 18:12 , <sknaugler@...> wrote:

Are there any types of lab power supplies that will inherently survive
back feeding from a battery if the line power fails, or you just turn it
off the wrong way?
Yes, the Farnell L30 series, very popular in the UK, have an internal diode
across the regulator in their 5A version, so they're absolutely fine with
being back-fed. But oddly the 2A and 1A variants don't have it.

I have a big HP 6031A (the 50V/60A/1000W one) which also seems tolerant of
being back-fed. At least I've done it lots of times with no adverse effect
so far.

Chris
Re: Need/want a bench top DC power supply.

 

In theory, you want a four quadrant power supply, one the both sinks and sources current.? An alternate name is an SMU (Source Measurement Unit) which may be designed to be a bit of overkill.

I'd suggest a box with a few analog meters, voltage and current, with a nicely big diode bridge.? Space the terminals so that it plugs into your power supply.? It would be relatively bomb proof. If I thought of it the right way, the bridge would keep the battery properly connected regardless of swapping terminals.

Harvey

On 12/17/2023 12:12 PM, sknaugler@... wrote:
Are there any types of lab power supplies that will inherently survive back feeding from a battery if the line power fails, or you just turn it off the wrong way?

Yes, I can always use a diode to prevent back feeding. I'd like to avoid that if possible because there may be that one time I forget, or don't have a diode with me.
Re: Need/want a bench top DC power supply.

 

I have a bridge on a heatsink with banana plug for the supply and red and black binding posts I use for any charging. I keep it near the supply. Safety precaution.

Peter

On Dec 17, 2023, at 12:12?PM, sknaugler@... wrote:

?Are there any types of lab power supplies that will inherently survive back feeding from a battery if the line power fails, or you just turn it off the wrong way?

Yes, I can always use a diode to prevent back feeding. I'd like to avoid that if possible because there may be that one time I forget, or don't have a diode with me.
Re: Need/want a bench top DC power supply.

 

Are there any types of lab power supplies that will inherently survive back feeding from a battery if the line power fails, or you just turn it off the wrong way?

Yes, I can always use a diode to prevent back feeding. I'd like to avoid that if possible because there may be that one time I forget, or don't have a diode with me.
Re: Need/want a bench top DC power supply.

 

Always be careful charging batteries from power supplies.? I have seen quite a few get destroyed if there is a power failure and are backfed by the battery.? If you are unsure and don't want to risk the supply place a sufficiently sized diode between supply and battery.

And if you accidentally connect a good sized battery backwards, consider your supply toast.

On 12/17/2023 9:51 AM, Torch wrote:
Korad KA3305P
Re: Need/want a bench top DC power supply.

 

Lots of options mentioned already.

I will throw out the Korad KA3305P linear supply for consideration.

Decent quality, Chinesium price. Three channels, but one is dedicated 5v so doesn't really count in this application. The other two can deliver 31v, 5.1a each all day long (variable, CC, CV, OCP, OVP, etc.); serial mode combines them into a single 62v, 5.1a supply (there's also a parallel mode to double the current instead). 5 memories to save settings.

One nice feature that might be of interest to you for battery charging: it's programmable via serial connection (MTTTY via RS232). You can log and/or change voltage and current automagically using available software or your own custom script. (NOTE: there is also a non-programmable version; same number without the "P" suffix)

I can't say I have ever used it to charge lithium batteries, but over the last ~8 years I have frequently used it to charge LA batteries. My only real complaint is the very large footprint. There's a fair bit of empty space in the cabinet.

Here's my original look at the innards on EEVBlog:

7704A - MOD3089

 

Can someone please tell me where I can find the details regarding MOD3089 for a 7704A? I was perusing one of the PDF scans of the service manual and notice there are several mods that seem to relate to the Guernsey versions of this scope, one of which is MOD3089 which changes R3468 to a 953-ohm resistor.

I have had problems getting the vertical positioning as close to correct as I can and one of the ways I did that was to place a 1k across R3468 (a 1.8k) which has helped that a bit. It makes the character height a bit smaller which keeps them both from being at the very top of the two graticule lines so I would be interested in knowing the details of that mod.

Thanks,
Barry - N4BUQ
Re: TDS520 in Brittany: FAIL++Acquisition FAIL++ Attn/Acq interface

 

Thanks Jared. Duly noted.
Yesterday I measured on J1400:
+15: +15.06
+5: +4.69
-5.1: -4.93
-15: -15.08
Ripple is less than 5mV.
I cleaned the boards prudently (ipa, brush & comp air). The PSU is something! My guess is it is outsourced by Tek?

I wanted to order caps with Mouser but was surprised to see they charge 20� p&p. Last time I ordered with them there was free shipping for orders above 50� ex vat.
Renaud
Re: Need/want a bench top DC power supply.

 

Hi Jim,

Yes, it is a robust design. Both designs use auto-sensed incremental Transformer tap ranges to provide an intelligent I-V SOA for the design.

The 6603D (Dual 60V 3A), I purchased before I rebuilt it, had a cooling fan failure that allowed it to damage Resistors and cause a fatal failure. After rebuilding it and the 6306A, they have been very good bench power Supplies.

Ross

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jim Ford
Sent: Friday, December 15, 2023 4:48 PM
To: [email protected]
Subject: Re: [TekScopes] Need/want a bench top DC power supply.

Got a Topward PS myself but don't recall the model number. It does have an issue with the master side not working, but I don't know how it was treated by its previous owner. Also, the red banana/binding posts have faded to an insipid pink. I will replace them eventually. I've opened it up (just in case it had those dreaded exploding RIFA caps; it didn't), and it's built like a tank! Very nice that the power xfmr is placed right in the center so it is well balanced. I'm impressed with the quality of design, and glad to own a nice piece of TE made in Taiwan and not in China. Jim Ford Sent from my T-Mobile 4G LTE Device
-------- Original message --------From: "si_emi_01 via groups.io" <wellington@...> Date: 12/14/23 9:37 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Need/want a bench top DC power supply. Hi,I use a Topward 6306A (Linear design, Separate Voltage and Current Analog Meters, Dual 30V @ 6A, 5V @ 5A), Topward 6603D (Linear design, Separate Voltage and Current Digital Meters, Dual 60V @ 3A, 5V @ 5A) as my main go-to Bench Supplies. I purchased them cheap and fully rebuilt them (including fans), they work well. You might consider something like that.I also have a Kikusui PAD-L 35-50 (Linear design, 35V @ 50A) and an HP 6032A (Switcher design, 60V @ 50A -1000 V-A) for bigger stuff.Ross-----Original Message-----From: [email protected] <[email protected]> On Behalf Of Mark LitwackSent: Thursday, December 14, 2023 7:58 AMTo: TekScopes@...: Re: [TekScopes] Need/want a bench top DC power supply.Sorry - Just noticed your price target in a later post. The Aim-TTi MX models are going to be quite a bit more than $100-$150.-mark
Re: TDS520 in Brittany: FAIL++Acquisition FAIL++ Attn/Acq interface

 

Don't bother buying a manual, head to Tekwiki where I've uploaded everything I can find for these scopes.



You'll only need to replace the VCO board if the two capacitors on the board have leaked a lot and damaged it. I have done one replacement, but other scopes didn't have enough leakage to need it. A visual inspection is enough, if you see corrosion of the traces, it's a small board so better safe than sorry IMO.

I leave the boards in to dry from the heater in the dishwasher, then blow out any remaining water from under the chips etc with canned air or an air compressor with the pressure turned down to avoid parts flying off the board.
Give it a few days and a blast with a hairdryer to be safe and you'll be fine.

Don't put the input hybrids through the dishwasher though! They are delicate and never need it anyway.



Jared
Re: tunnel diode orientation in Type 284

 

Awesome glad to hear the 284 is back up and pulsing.

Zen

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Shaun M
Sent: Friday, December 15, 2023 10:10 AM
To: [email protected]
Subject: Re: [TekScopes] tunnel diode orientation in Type 284

Adam,

Well done! Now on to the next project……..


Shaun M.
Re: Need/want a bench top DC power supply.

 

On Thu, Dec 14, 2023 at 04:54 AM, Peter Gottlieb wrote:


As an alternative for coarse and fine adjustment knobs consider a single 10
turn
pot.? I've actually retrofitted several older power supplies this way and it
works pretty well.

I'm curious, what do you need high resolution for on the metering?
The 10 turn pot is a good way to side step the need for dual (coarse and fine) pots. I used to have (20+ years ago) an ancient vacuum tube dual power supply with 10 turn pots, but to avoid moving that behemoth I gave it to a friend.

I like the digital meters for convenience. For example, on the Sorenson LH 60-6 one day I would use 24 V, which would be easy to read on a 60V range analog meter. The next day I would need 1.2 V, not so easy to read on that same 60V analog meter. The Sorenson's digital display was just easier to use, although for critical work I would use a second meter to double check the built in.
Re: Need/want a bench top DC power supply.

 

Got a Topward PS myself but don't recall the model number.? It does have an issue with the master side not working, but I don't know how it was treated by its previous owner.? Also, the red banana/binding posts have faded to an insipid pink.? I will replace them eventually.? I've opened it up (just in case it had those dreaded exploding RIFA caps; it didn't), and it's built like a tank!? Very nice that the power xfmr is placed right in the center so it is well balanced.? I'm impressed with the quality of design, and glad to own a nice piece of TE made in Taiwan and not in China.? ? ? ? Jim Ford?Sent from my T-Mobile 4G LTE Device

-------- Original message --------From: "si_emi_01 via groups.io" <wellington@...> Date: 12/14/23 9:37 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] Need/want a bench top DC power supply. Hi,I use a Topward 6306A (Linear design, Separate Voltage and Current Analog Meters, Dual 30V @ 6A, 5V @ 5A), Topward 6603D (Linear design, Separate Voltage and Current Digital Meters, Dual 60V @ 3A, 5V @ 5A) as my main go-to Bench Supplies. I purchased them cheap and fully rebuilt them (including fans), they work well. You might consider something like that.I also have a Kikusui PAD-L 35-50 (Linear design, 35V @ 50A) and an HP 6032A (Switcher design, 60V @ 50A -1000 V-A) for bigger stuff.Ross-----Original Message-----From: [email protected] <[email protected]> On Behalf Of Mark LitwackSent: Thursday, December 14, 2023 7:58 AMTo: TekScopes@...: Re: [TekScopes] Need/want a bench top DC power supply.Sorry - Just noticed your price target in a later post.? The Aim-TTi MX models are going to be quite a bit more than $100-$150.-mark
Re: tunnel diode orientation in Type 284

 

Adam,

Well done! Now on to the next project……..


Shaun M.
Re: tunnel diode orientation in Type 284

 

On Dec 15, 2023, at 04:26 , Albert Otten <aodiversen@...> wrote:

Remains the key question: did you change the orientation of the TD an odd or an even number of times? Perhaps there was nothing wrong at all with the 284 except setting of the bias controls.
An even number, and I hope to never use tweezers on that TD again. There was nothing wrong with the 284 except the coarse bias control and dirty slide switch contacts.

I also note that I screwed up the rise time measurement level; it's closer to 1.1 nS on the 2465A.

And now a sampling scope to verify the outputs of the 284 will be on your wish list....
Of course, but when my wife asked what this fast pulse was useful for, somehow "justifying another scope" wasn't on the list.

thanks,
Adam
Re: tunnel diode orientation in Type 284

 

Hi Adam,

Nice that your pulse output is OK now!
Remains the key question: did you change the orientation of the TD an odd or an even number of times? Perhaps there was nothing wrong at all with the 284 except setting of the bias controls.
And now a sampling scope to verify the outputs of the 284 will be on your wish list....
About manual versions: one advantage of a more recent manual is the use of more modern equipment in the calibration procedure.

Albert
Re: TDS520 in Brittany: FAIL++Acquisition FAIL++ Attn/Acq interface

 

Thanks to you both. Yes my intention was to:
Buy the manual
Measure the psus
Desolder and take notes of caps data.
Clean the boards. I will indeed put them in the dishwasher Jared. I would not have dared but now I will. How long that will take to dry I wonder?
Look with a magnifier at the traces.
Recap with Nichicon 105 deg low z caps. Good price when ordered by hundreds!

I understand the rom is a bios and I documented it in case the firmware was any use.
What is the frequency covering of the vco? From the L101 I'd guess GHz.
What makes you think I will have to replace it Jared?
Thanks,
Re: tunnel diode orientation in Type 284

 

My Type 284 now has a working pulse, and my sincere thanks to all who have helped with this problem! One lesson learned (maybe): start checking signal levels versus the manual before taking stuff apart randomly. Another might be to look for a newer version of the manual.

The coarse bias adjustment did the trick, and pretty easily got the arming pulse voltage high enough. I can sure see why they went to a finer control, because it's pretty twitchy.

Proof of life:



I think the list frowns on using the variable attenuator to measure rise time, but this seems about right for a 350 MHz scope. I'm using 42" RG58 cables, so not ideal.



For extra fun, the 1 GHz sine is barely visible, and the scope actually seems to trigger on it. I do wish I could get a bit more intensity out of the scope.

<>

Next project is to calibrate my 475, which has pretty bad overshoot on fast edges, and I think it's lying. I ran into this making a homebrew GPSDO, and it's been really annoying. Here's the 284 pulse on that scope:



thanks,
Adam
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