REPLACEMENT FOR MM5369 TIMEBASE CHIP

[jimandy]

Robert R., "exceedingly" surprisingly" - whatever, My question goes to the time-base reference they use. Where/how does it originate? Is there a little quartz crystal with count-down circuit keeping it all humming?

To craig-1. The Bham Library on-line catalog says they have some issues in the year range you're asking about. I'll check it out, but past history suggests that a lot of catalog items like that have walked out.

[craig-1]

I want to THANK every one who responded to my request for a timebase replacement for the MM5369 chip. NUTS & VOLTS readers gave me two working circuits that I can use for a timebase of 1Hz and 0.1Hz. I just want to thank you all for responing. If anybody every need a timebase replacement for the MM5369 chip contact me at [email protected] and I will send them the same info. that I received. A SASE envelope will help, THANKS CKS

[Robert Reed]

Jimandy
I spent some time several years back in the control room of a local power plant. It was an older power plant with a 600 Mwatt output capacity. It was interesting to see the operator phase in the generator when coming on line-with 120v lightbulbs! All plant and system bus voltages (including the grid) are ratioed down to 120VAC (thru what are known as potential transfomers- PT's),which is a utility company standard for I & C. Once the generator was broght up to proper voltage ,the lamps were viewed. These were connected between generator and grid thru PT's.Then the generator frequency was raised or lowered until a visable flashing could be seen. Adjustment slowly continued to the point where flashing slowed and came to a point where the bulbs extinguished. At that point the generator frequency not only matched the grid but was in phase with it and the generator was closed into the system.
As far as maintaining frequency, heres how it was explained to me and it sounds very plausible. Large distribution regions are controlled by their respective committee's. These committees monitor system frquency among a lot of other parameters,with highly accurate frequency recorders that not only measure error but the duration of the error. Periodically, a correction command is sent to the participating power plants, Thru a system called Automatic Generator Control (AGC).The time base for this system is eventually linked to NIST probably via GPS satellites with todays hi-tech gear. The command is issued not only to correct the error but to overshoot it for the specified time that the error existed and then return to normal thereby producing the long term accuracy by means of averaging. The error signal then adjusts turbine pressure or feild current until the system is satisfied (think of it as a huge servo system)These machines are huge and do take some time to respond, so this is not and instantaneous process. This is a simplification of what is happening as this is a PID process and has much more involved than simple feedback. The control room also had its own monitoring equipment , although to a lesser degree and could over ride the AGC system should that become neccessary.
My prior ideas of the grid was simply power being dumped in at various points and power being taken out at different points. But after spending a considerable amount of time at this and other plants in the system I learned that it was an extremely complex process to keep it functioning properly. Humoungus and powerful and yet very vulnerable.

[jimandy]

(robert reed)

...very vulnerable

A few years before 9/11, I drove down with my kids to one of Ala. Power’s early hydro electric dam facilities. There was no one there, I mean NO one except the security guard who came out to chat. He talked a bit and then, apparently happy to have visitors, volunteered to take us down to the power room. There we saw the large generators, and he told us the bearings for the turbines were the original ones made from a certain type of wood that was virtually indestructable. He then took us in the control room which was full of ancient switches, meters and the like.

I remarked how eerie it was to see all these controls and no one there running the plant. He explained it was all controlled from Birmingham, 100 miles away. I asked why then was all the old control room equipment still there. He said, “well, just in case...”
His voice trailed off without completing the sentence.

[L. Daniel Rosa]

Lignum vitae? I've heard of it being used for bearings. I have a chunk of it in the garage. Won't rot, won't float.

[Robert Reed]

Lignum Vitae for sure. Vitually all the early steam powered ships and even Deisel powered somewhat later used this wood for the propeller shaft bearings. I hear it is still used occasionally today.

[Yerry]

I noticed this thread a little late, but I wanted to comment on chip operation.

Looking back at my two-way-radio reapir days in LA, Motorola-designed frequency-generation chips (an entire series of divide-by-n and integrated PLL chips) that were desined to work together in a multi-step scheme.

The generated frequency was divided by a number that would take it closest to the time interval (1/freq) of the reference oscillator without actually exceeding it. (there's a "remainder" here) Then another counter chain would count an appropriate number (predetermined) of generated freq cycles until the time base was correct. Then, the two signals are compared in a PLL scheme, and the appropriate "charge punmp up" and "charge pump down" (which would have made more sense as "discharge pump")to the PLL oscillator to keep the frequency correct. Other divide by n chips could be used in either the reference of generated oscillator chains to makae the electronic math simpler.

When troubleshooting, I would look for as many as three dividor chips turning on and off in various combinations; my boss had a not-so-great o-scope that could barely pick up the square waves. It was like studying a ghost for facial details!

So, the 60-Hz oscilator, designed NOT to need any user-changable parameters, doesn't need to be a divisible down to 60.

[Robert Reed]

Yerry
In reading your comments on PLL chips, I to was reminded of my Motorola days, This PLL system was designed by a brilliant engineer back in the late seventies. Of all the shcemes I have seen, this was the greatest--a counter that could divide by fractional numbers, even deep fractions. It used two counters-A divide by` A' counter and a divide by` N' counter. These were preset by thumbwheel control for any desired frequency. The counters started there down counting simultaneously and when the` A' counter reached its preset value, it would reset a dual modulus prescaler to a new divide by ratio (usually only one or a few division ratios different), The divde by `N' counter still ticking down would now see a new prescaler value. This whole process can be written out mathematically. Just imagine dividing any given frequency by 173.1143, and you can appreciate this design. Forgive me for rambling on, but your reply did trigger my memory of one the most fantastic circuits since Englands " Phantastron " Circuit ,which I beleive was back in the early `50s and before my time.

<small>[ December 07, 2005, 09:06 PM: Message edited by: ROBERT REED ]</small>

[craig-1]

Robert Reed; I have a question what is a PHANTASTRON circuit?
Go to the following website http://www.elmelectronics.com and you will find a substrtute for the National Semiconductor MM5369 CHIP it's the ELM440 CHIP which drectely replaces the MM5369. ELM also has a replacement for the 50Hz chip MM5368
Craig

[rshayes]

The "phantastron" circuit was actually developed in the early 1940's. It provided a time delay from a trigger pulse that was controlled by a voltage. The delay was an accurate and linear function of the control voltage. It was used in radar systems to measure the range of a target detected by the radar set. The delayed pulse provided by the phantastron could be mixed into the radar video, producing a step which indicated range. The step was adjusted to coincide with the return pulse from a target.

The original circuit used one pentode tube. It was normally in an idle state, but when triggered by a pulse, it acted in a linear fashion producing a negative going ramp that was very linear. When the ramp reached an end point, the linear operation ceased and the circuit reset itself to the idle state. The starting voltage of the ramp could be varied to vary the time until the end of the ramp.

Previously, this function had needed several tubes, so this circuit was considered very useful.

[Robert Reed]

Stephan
Glad to hear of someone else out there who knows of this.Hope we aren't dating ourselves Its been a long time since I have seen this circuit in schematic form. It was unlike any vaccuum tube layout I had ever seen--almost crazy? If memory serves me correct, it was inputted thru the screen grid and outputted from the control grid. I think Miller effect played a major role in its operation.

[rshayes]

I don't know if the inventor of the transitron circuit is even known. Whoever it was, he certainly had a warped mind and may have been a genius. Or the invention may have been an accident.

One unusual feature was using the supressor grid as a control grid. If the supressor was made negative, plate current would be diverted to the screen grid. If the screen circuit had a load resistor, this increased screen current would cause the screen voltage to fall. In the transitron and phantastron circuits, the screen was coupled to the supressor. This caused positive feedback and resulted in the circuit latching in one of two states, with either full plate current or cut off plate current.

In the phantastron, the plate was coupled to the control grid by a timing capacitor. A large value timing resistor was also connected between the control grid and a positive voltage. This formed a Miller integrator when plate current was flowing.

In the idle condition, the plate current was cut off and the current through the timing resistor biased the control grid slightly positive. This resulted in high screen current, low screen voltage, and a negative voltage on the supressor grid, which cut off the plate current, resulting in a high plate voltage.

If a positive pulse was applied to the screen or supressor grid, some of the screen current was diverted to the plate, causing a positive step in the screen voltage and a negative step in the plate voltage. This action was regenerative due to the coupling between the screen and suppresor grids. As the plat voltage fell, the control grid voltage also fell, due to coupling through the timing capacitor. This formed a negative feedback path, which stabilized the plate voltage at the level initially on the timing capacitor.

The timing current flowing through the resistor from a positive voltage to the grid caused the timing capacitor voltage and plate voltage to decrease in a linear ramp. This ramp was very linear due to the Miller effect.

Eventually, the plate voltage dropped to a point where the plate current could no longer increase. At this point, the screen grid current started to increase. This caused the screen voltage to decrease and this decrease was coupled to the supressor grid, which caused the plate current to decrease. Again, this effect was regenerative untill the plate current was cut off and the circuit returned to its initial idle state.

This circuit combines both digital and analog operation. The switching of current between the screen and the plate is bistable. The magnitude of this current is a variable voltage signal which forms a linear ramp.

Variable delays were obtained by using a diode to limit the voltage on the plate when the plate current was cut off. The lower the voltage the the plate was clamped at, the shorter the time delay.

The British pentode originally used had a supressor grid wound with an exceptionally narrow spacing. No American tubes were made that way, so the circuit was adapted to heptode tubes such as the 6SA7. The third grid was used instead of the supressor to control the division of current between the screen grids (2 and 4) and the plate. The fifth grid was used in the normal way as a suppressor grid.

[Robert Reed]

I guess what it all came down to was with the amount of power consumption and chassis real estate that tube cicuits took up, one had to be quite inventive in their designs. As witnessed by the "6 tube wonder"- the Muntz TV !
BTW- an exellent explanation Stephan.

<small>[ December 08, 2005, 08:53 PM: Message edited by: ROBERT REED ]</small>

[philba]

Originally posted by ROBERT REED:
I guess what it all came down to was with the amount of power consumption and chassis real estate that tube cicuits took up, one had to be quite inventive in their designs. As witnessed by the "6 tube wonder"- the Muntz TV !
BTW- an exellent explanation Stephan.

No kidding. I have an old Atwater-Kent radio I'm restoring and they did some quite clever hacks to minimize the component count. My favorite was they avoided a permanent magnet speaker by using an electro magnet ("speaker bias coil"). Guess what they used for the choke on the rectifier circuit - the speaker bias coil. What suprises me is there is no hum.

[Robert Reed]

The old timers referred to these as "hum-bucking coils".