Path: /eico/b/. This is the BAMA archive. These manuals are Files: brozokpulepsmen.cf ( KB) brozokpulepsmen.cf (4 MB ). Download EICO B CONSTRUCTION MANUAL. service manual & repair info for this is not a pdf file. pdf, but possible corrupted, or password protected. large a signal is fed to the control grid of the tube. By using the maximum opening method, more sensitivity and accuracy is obtained. The expanded capacitance.
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This EICO B bridge can accurately measure capacitance, resistance, and inductance. It also can check a capacitor under its actual operating voltage. EICO initiated the development of the new tube type 12DW7. • Dramatic high styling EICO's new dramatic series of stereo hi-fi com- ponents establishes a new. Eico: eico model b bridge construction. Identifier: eico_eico_model_b_bridge_construction. Identifier-ark: ark://t5jb03b28 .
It is unnecessary ta use the comparator range for measurement of resistances andcafkicitances falling into the direct measurement range of the instrument. The capacitor in both tests Is connected across the right-hand binding posts just os in ccpocitonce measurements. Be certain that the positive lead of on electrolytic capacitor is connected to thebinding post morked plus and the negative lead to thebind- Tng post marked minus. Otherwise, notoniywlii the leakage test hove no.
Observe the electron- ray tube and note that the shadow angle is at maximum, which is the "normal" Or "no-leakage" indication in the leakage tests. The shodow angle should contract instantaneously as the capacitor charges and thenslowly expand. If the shadow ongle completely disappears and does not reoppear, the capacitor is excrasively leaky. The shodow angle need not expand to the maximum as before in order for the copacitor to check good.
As these tests ore very sensitive, a little leakage in capacitors with values above. This is normal with a good capacitor and the reappaoronce of even a very small shadow ongle meons that the capacitor Is good.
Only complete failure of the shadow ongle to reoppear indicate an excessively leaky capacitor. When making the leakage test, enough time must beollowed for theleokage current to reoch the normal value.
The instructions of the capacitor monufactureis are to measure the leakage current of the ca- pacitor at the roted de voltage, after the rated dc voltoge has been applied to the capacitor for five minutes plus one minute for each month of she if storage. In each of the bridge circuits PI varies the resistorice in two arms. The 54 volt winding is the secondary winding of the power transformer that supplys the ac power to operate the bridge.
R1 is o current limiting resistor. The B plus voltage required to power the electron-roy indicator and the neg- ative dc valtoge required For leakage testing of capacitors ore obtained from the 6X5 tube Vi connected os a half-wove rectifier, in conjunction with the high voltage secondary winding of the power transformer and the filter and voltage divider networks composed cf R8, R7, P3, Ct and C9, NOTE: The electron-ray indicator is preferable taheadphane or a meter since It may be used without disturbonce from external noises and is capable of withstanding substantial overloading without damage.
Bridge circuit for "lOmmfd - mmfd" range C2 and ". Bridge circuit for ". Imfd - 50mfd" range.
R2 expands copacitonce measurement range as compared to circuit of Fig. R2 expands resistance meosurement range as compared to circuit of Fig, 4. R9 slows down charging process so thot electron-roy tube action will not be too fast for detection by the operator. Nate that R1 1 ,2.
Stockf Svm. Descriptcon Am' Cl cap. The Eico provides the ratio between the two, a handy feature indeed! The ratio test can also be used to determine turns ratio of laminated transformers such as audio and interstage transformers.
With two identical caps or resistors, the comparator function should be dead center at a ratio of 1. If the pointer does not show 1, the 10 K pot used for the main dial may be off a bit.
Add a small resistance to one side of the pot or the other. A small variable resistor can be used. I just cheated with one of the B sets and moved the pointer just a bit to the center since the extremes of the dial are not that accurate anyway. Eico B quad High voltage and leakage tests Like the A, the Eico B uses a high voltage supply of about volts with two electrolytics in series.
If its 68K resistor has drifted high, the tuning eye will see voltage higher than relative to chassis and the test voltage the high B- will see that equivalent amount subtracted from You will be unlikely to find the correct voltages even with an exact 68K resistor since there are variations in the power draw of various tuning eye tubes. A tuning eye should not be subjected to more than about volts.
I tried to balance the voltages in one B and settled on a resistor of 62K to achieve a compromise to reduce the tuning eye voltage to about volts. The voltages are, of course, partly dependent upon line voltage. Leakage current The Eico B has a K resistor in the circuit to measure leakage of "paper and mica" capacitors.
I found that the B closes its eye tube at an average leakage current of about 15 uA microamps with variations ranging from 13 to 17 uA. The leakage figure is partly affected by variations among eye tubes. I measured the K resistor in each of the B. If that resistor had drifted high typical , I left it in place because that would reduce the leakage current necessary to close the eye.
I personally find a leakage allowance of 15uA for non-electrolytic caps to be too high. Later Heathkits below use the figure of 2uA maximum as a cutoff point for leaky paper and mica caps and provide an onboard control to set the eye tube closure at that point. The maximum for electrolytic leakage is typically set at 2 mA in later Heathkits.
The Eico B uses a 2. I found that the average leakage current to close the eye was about 3 mA. Again, if the 2. Testing for leakage current So how can you check the mica-paper leakage current needed to close the tuning eye of an Eico without using a microammeter? I used my cheap 1 megohm input digital meter from Harbor Freight and set it for DC voltage.
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The highest scale volts is fine. I connected the meter across the two terminals in place of a cap and slowly turned up the voltage pot. When the eye just barely closed, I read the voltage.
That's the uA leakage. The cheap meter read the microamps directly because it presents a constant 1 megohm load.
My higher quality 10 megohm digital meter was connected the same way. In that case, I simply divided the voltage by 10 to get the uA reading. The electrolytic leakage point was determined by resetting the digital meter to milliamps such as the 20 mA scale on the low-end Harbor Freight meter. I adjusted the voltage upward until the eye just closed and then read the meter making sure that the meter never exceeded 4 mA to avoid overloading the Eico's voltage control. Don't know whether your digital meter is 1 meg input or 10 meg?
Put the digital meter on its high DC range and use the cap tester to read its resistance on the bridge directly or use that external comparator input against a 1 meg or 10 meg resistor! Caution on testing aluminum shell electrolytics with all of these capacitor checkers that use the split voltage supply The positive connection to a capacitor under test is at or within a few volts of the chassis but the negative side of the test voltage can be hundreds of volts negative with respect to the chassis.
That means when leakage testing or reforming those aluminum shell electrolytics, there can be several hundred volts between that aluminum shell and the cap tester chassis.
The IT was introduced in The IT followed in and was reportedly available until , a 16 year run for the overall design. The Heathkits limit the bridge voltage to 12 volts AC versus the Eicos at 55 volts. Heath uses a third tube to amplify and rectify the bridge voltage.
The Heath design also has an additional leakage setting for low voltage electrolytics of the transistor era. The Heath has three on-board pots to adjust the leakage settings for accuracy.
The Heath uses divider resistors for accurate preset voltage as compared to a single pot with marked but often inaccurate voltage settings.
The Heath has a lever to select for bridge or leakage but adds that all-important discharge setting between the two. That setting dumps the electrolytic charge into a 10K ohm 10 watt resistor as opposed to turning down the voltage pot and using its resistance to discharge the cap. The Heath uses a single high voltage with the chassis at B- ground thus avoiding the hazard described above that is inherent in the split voltage testers. Also, a shorted cap will not burn out the eye tube but may blow the fuse which the Heath has but the Eico does not.
The Heath has the comparator connections like the Eico but also has terminals for connecting an outboard signal or function generator for more accurate readings of small caps and comparator-connected inductances. The IT upgrades the power cord to a three wire grounded version, has a spring-clamp on the tube socket for the 6AX4 rectifer, uses modern caps for standards, and has a power transformer with dual primary windings that can be rewired for volts. However, it also has push-on knobs that cannot easily be re-adjusted as compared to the IT with set-screw knobs.
To reset the pointer just a bit on the IT main dial, I found it easier to loosen the main pot and tighten it again rather than to change the pointer on the knob. Repairs on the Heathkit IT and IT The first act on either of these after safety checks is a good application of deoxit to all the controls and switches and the 6BN8 tube socket.
I did not immediately apply deoxit to the 6BN8 pins in the IT and was greeted with a cold filament in that tube. The cold filament was due to poor pin to socket connections, a problem quickly solved with the deoxit cleaner. The electrolytics were in good shape as well. I carefully matched a pair of tested 0. That brought the capacitance bridge to very good accuracy. However, the range that uses the 2 MFD cap showed only a very narrow opening of the eye tube.
Then it dawned on me that the only item in that circuit that was not part of the other ranges was the power factor control. Sure enough, the power factor control was open at what should have been the grounded end. More deoxit did not cure it. I opened the control and found the problem. The center contact was not quite level.
A quick adjustment with needle nose pliers cured it. The IT did not need repairs other than the deoxit treatment.
Leakage adjustment pots Setting the leakage eye-close points Both the IT and the IT were well off the mark for the leakage set points.
Eico: eico model 950b bridge construction
The three on-board controls that adjust those points must be set in the proper order with the 2 mA setting for electrolytics first adjustment pot is at the top followed by the small electrolytic adjustment for 15 uA pot is at the bottom and finally the 2 uA setting for paper and mica caps pot is in the center. Accuracy of the adjustments can be partly affected by changes in line voltage.
Comparing 2 chokes with a Heath IT Note that the indication on the eye-tube is not as pronounced as with cap or resistor comparisons Comparisons The Eico A and B are more versatile and useful than the early Knight, Lafayette and Heathkit offerings.
I especially like the very simple 2 mA leakage circuit of the A using just two resistors and a neon bulb. The B has a more robust voltage control than the A. However, the later Heathkits are obviously more capable than the Eicos and a bit safer when testing aluminum shell electrolytics. The lack of a meter is easily overlooked once one is confident of the repeatable voltage settings and the accuracy of the adjustable leakage settings.
The comparator feature is a real plus in either choice, but the ability to hook an external generator is unique to the Heathkits. They are still very usable if performing at their full capability. If you can find a functioning one near its original price, grab it. The Eico and other testers can be modified with larger resistors or even an on-board control pot to make them more sensitive for leakage.
Here is a link to Bob Putnak's useful web page where he has done exactly that. The Heathkit IT manual is still protected by copyright since it was written after The IT manual, however, had a publication date that was obviously prior to Like most of its manuals, Heath never renewed the IT manual copyright, a requirement for continued copyright protection for publications prior to The manual is therefore in the public domain.
One possible source is mods.
Power Factor and ESR Looking through the manuals of tube-era capacitor analyzers, you quickly realize that the term "power factor" is in fact a way of expressing ESR equivalent series resistance at a frequency of 60 Hz.The main electrolytic is very high voltage volt and really needs two 22 mfd volt units mounted in series, with say k resistors across each one to replace it properly. So tomorrow I get to make the rounds of the electronics parts houses as few and far between as they are and hope someone has it.
Set the Range switch to ". Like most of its manuals, Heath never renewed the IT manual copyright, a requirement for continued copyright protection for publications prior to Furthermore, micas and ceramics are often found in tuned circuits where precision is crucial. If the crescent remains closed all the way when you reach the rated voltage, the cap is too leaky to use. The Heath design also has an additional leakage setting for low voltage electrolytics of the transistor era.
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