Author Topic: Frequency counter won't count.  (Read 23315 times)

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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #50 on: July 08, 2017, 03:45:08 am »
I cannot make much sense of the schematic for the +5V regulator board, it took me a long time to even find the schematic.  :palm:
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 

Offline Cubdriver

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Re: Frequency counter won't count.
« Reply #51 on: July 08, 2017, 04:45:43 am »
That seems like an awful lot of ripple on a 5V logic power supply line.  A suggestion for seeing just the ripple - AC couple the scope input.  That will get rid of the DC level and let you see only the ripple, and make it easier to measure.

I'm going to try to excavate my manual and get mine onto the bench.  Perhaps I'll be able to help hunt things down with you.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #52 on: July 08, 2017, 04:58:25 am »
If you can't identify the actual filter cap, just connect a known good one of some reasonable size from the regulator input to ground (watch polarity) and look for an improvement in the ripple.

Didn't work, i also tried putting a capacitor on the output and that reduced the ripple slightly. I used a 3500uf cap.
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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #53 on: July 08, 2017, 05:09:30 am »
I put a capacitor on 5V DG output and it worked, it started counting again. The scope probe is set to 1x and AC , the center line on screen is center line of voltage present.

1st  shot, 10v scale.

2nd shot,  2v scale.
« Last Edit: July 08, 2017, 05:11:46 am by neo »
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Offline Cubdriver

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Re: Frequency counter won't count.
« Reply #54 on: July 08, 2017, 05:14:17 am »
Sounds like a bum cap on the digital power supply, then.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #55 on: July 08, 2017, 05:31:18 am »
This is it on  20 mv range with 50,000 uf capacitance, am i the only that thinks this problem can be solved with a super capacitor?
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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #56 on: July 08, 2017, 05:43:35 am »
Now that the power supply is at least under control it will only show 3 digits when counting, i have it on self check and in resolution scale of;
1 it reads        .001 KHz;
10 it reads      0.00 KHz;
100 it reads    00.0 KHz;
1k it reads      .000 MHz;
10k it reads    0.01 MHz;
100k it reads  10.0 MHz;
1m it reads     .010 GHz:

The left 4 will flash 0 when i change ranges but that is it, otherwise they are off.
« Last Edit: July 08, 2017, 05:54:37 am by neo »
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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #57 on: July 08, 2017, 06:02:44 am »
After being mildly agreeable for a couple of minutes it did this. 1x probe ac coupled and on .2V range. Still allows it to count though.
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Offline Cubdriver

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Re: Frequency counter won't count.
« Reply #58 on: July 08, 2017, 06:17:34 am »
 |O |O |O  I had a long reply typed up and the effing webpage just gorked and ate it.   |O |O |O |O

I'm looking at the +/-5V digital supply schematic (fig. 8-34) on page 8-75 of the manual I have here.  The +/- 5V digital supplies are fed from a bridge rectifier (CR1) that, combined with the center tapped transformer secondary it's fed from is configured as a pair (positive and negative) of full wave center tapped rectifiers.  The resulting positive and negative rails are filtered by A30C5 (+) and A30C6 (-).  Based on the A30 board drawing on pg 8-73, it looks like A30C5 & 6 are the two rearmost of the '6 pack' of filter caps there adjacent to the regulator boards.  The left rear one is A30C5, and the right rear one is A30C6.  They are 4000uF, 15V (page 6-27 in the parts list).

Hope this helps a bit.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline Cubdriver

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Re: Frequency counter won't count.
« Reply #59 on: July 08, 2017, 06:18:57 am »
After being mildly agreeable for a couple of minutes it did this. 1x probe ac coupled and on .2V range. Still allows it to count though.

I'm curious - where are you connecting the probe to pick this up?  TP2 on the A32 board?

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #60 on: July 08, 2017, 06:27:26 am »
After being mildly agreeable for a couple of minutes it did this. 1x probe ac coupled and on .2V range. Still allows it to count though.

I'm curious - where are you connecting the probe to pick this up?  TP2 on the A32 board?

-Pat

Yes i am. Why?
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Offline Cubdriver

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Re: Frequency counter won't count.
« Reply #61 on: July 08, 2017, 06:30:06 am »
After being mildly agreeable for a couple of minutes it did this. 1x probe ac coupled and on .2V range. Still allows it to count though.

I'm curious - where are you connecting the probe to pick this up?  TP2 on the A32 board?

-Pat

Yes i am. Why?

Just wanted to be sure I knew the source.  What is the frequency of the ripple - how much time for each cycle?
If it jams, force it.  If it breaks, you needed a new one anyway...
 

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #62 on: July 08, 2017, 06:40:12 am »
120 Hz, the last shot was actually 10x sorry for the confusion.
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Offline Cubdriver

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Re: Frequency counter won't count.
« Reply #63 on: July 08, 2017, 06:54:49 am »
120 Hz, the last shot was actually 10x sorry for the confusion.

Darn!!  I was hoping you'd say 60, which could have meant one of the rectifiers was failing.  So much for that brilliant idea!

Are you putting your additional filter capacitance across the actual filter cap, or directly on the regulated output?  If directly on the output, it could be confusing the regulator by messing up the response time of the control loop.  If you have it across A30C5, then never mind; if not and it is on or near the output and beyond the regulator pass transistor, try to get it onto C5 instead where the circuit expects to have filtration.  That might help things out.

And on that note, I really need to crawl off to bed - it's 0300 here in these parts.  Good luck, and I'll try to offer more suggestions tomorrow if it's still acting up.

-Pat
If it jams, force it.  If it breaks, you needed a new one anyway...
 
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Offline TheSteve

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Re: Frequency counter won't count.
« Reply #64 on: July 08, 2017, 06:59:50 am »
I have two 5340A's. Both of the Nixie tube vintage. I still say replace all 6 of those caps. The original's are snap caps which are very expensive to replace but you can get cheaper replacements that fit just fine with a little soldering. I liked that the originals bolted in but the cost(and smell) of the originals made up my mind for me.
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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #65 on: July 08, 2017, 07:12:16 am »
I have two 5340A's. Both of the Nixie tube vintage. I still say replace all 6 of those caps. The original's are snap caps which are very expensive to replace but you can get cheaper replacements that fit just fine with a little soldering. I liked that the originals bolted in but the cost(and smell) of the originals made up my mind for me.

I quite like the way those caps mount to it as well and i am not discounting your advice to replace them it is just that i would have to buy them as i don't have any.
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #66 on: July 08, 2017, 07:25:46 am »
I dare say that is approaching reasonable, 55,000 uf in parallel with C5 1x probe (i checked to make sure) 20mv scale.
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Offline rdl

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Re: Frequency counter won't count.
« Reply #67 on: July 08, 2017, 08:05:34 am »
55,000 uF ? !!! With that much filter capacitance you probably don't even need a regulator.
 

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #68 on: July 08, 2017, 08:08:00 am »
As little as 4000uf makes a difference so  i guess i will have to replace the caps

http://www.ebay.com/itm/112056031209?var=410994326596 15000 uf version of these for C5 and C6 work?
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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #69 on: July 08, 2017, 08:10:03 am »
55,000 uF ? !!! With that much filter capacitance you probably don't even need a regulator.

That was as a test i reduced it to 4000 uf, just like spec, and it remained happy
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Offline TheSteve

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Re: Frequency counter won't count.
« Reply #70 on: July 08, 2017, 08:14:16 am »
I used Digikey part # 338-1626-ND
VE7FM
 
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Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #71 on: July 08, 2017, 08:16:13 am »
I used Digikey part # 338-1626-ND

Does it fit the same as the originals?
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Offline TheSteve

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Re: Frequency counter won't count.
« Reply #72 on: July 08, 2017, 08:20:07 am »
They nicely fit in place of the originals, but do have to be soldered.
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Offline RoGeorge

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Re: Frequency counter won't count.
« Reply #73 on: July 08, 2017, 08:21:30 am »
120 Hz, the last shot was actually 10x sorry for the confusion.

Darn!!  I was hoping you'd say 60, which could have meant one of the rectifiers was failing.  So much for that brilliant idea!

A bridge rectified 60Hz is 120Hz.

Offline neoTopic starter

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Re: Frequency counter won't count.
« Reply #74 on: July 08, 2017, 08:22:23 am »
They nicely fit in place of the originals, but do have to be soldered.

I will have to bodge something in temporally though those will work nicely. Any thoughts about the display only giving me 3 digit resolution?
A hopeless addict (and slave) to TEA and a firm believer that high frequency is little more than modern hoodoo.
 


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