Scott-LK-48-Assembly-Manual 电路图 维修手册.pdf

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1、INSTRUCTION 1.EA10 fear of damaging your amplifier. We have often referred to the desirability of low distortion. A wide frequency response, ample power, and low hum and noise are important but cannot com- pensate for high distortion. The LK-48 will produce its rated outpt1t of 24 watts (IBFM standa

2、rd) at less than 0.8% total harmonic distortion. This is important, but even more important is the distortion at normal listening levels. Many amplifiers will exhibit reasonably low distortion at full output, but actually turn out to hnve as much or more distortion at normal listening levels of 1 co

3、 5 watts. T his is self-defeating. At norrnal listening levels, the total harmonic distor- cion of the LK-48 is below 0.05%, which means it is so low it cannot be accurately measured with even the finest of laboratory instruments! The translucent sound from your LK-48.is proof of this low distortion

4、. Power Supply In order to supply the necessary voltages to all the stages of the amplifier a rugged power supply is needed. The husky oversize power transformer along with the GZ34/5AR4 rectifier and SRI selenium rectifier com- prise the heart of the power supply. An important charncceristic of the

5、 GZ34 is its slow warmup. This gives the other tubes and components nn opportunity to reach normal operating condition before the foll force of the high voltages and currents are transmitted by the rectifier. T he electrolytics ( condenser cans) arc all specially designed and conservatively operated

6、. These are other factors in the long life you cnn expect from the amplifier. Heat can be a problem in any high power amplifier. Under normal conditions you can expect the amplifier to use about 200 watts of electricity. This will generate a considerable amount of heat. The heat has to be rapidly tr

7、ansferred a way from the output stages where most of it is generated. If ir is not, the life of the tubes :ind other components will be greatly curtailed. One of the w.1ys the heat is carried away is by convection to the air. The many holes in the chassis are designed co encouraoe air circulation wh

8、ich well perform this func- tion. Ecially important is the use of electrolytic alumi- num for the chassis material. Most amplifier chassis are steel which is a less expen- sive material. Unfortunately steel is not a good con- ductor of heat so such units will have their output scages ovcrhenting eve

9、n though the rest of the amplifier is cool. Aluminum is an excellent conductor of heat, so it rapidly conducts the heat away from oncput stages to ocher parts of the chassis where it can be readily transferred to the air. In fact you may notice that your aluminum front panel is warm to the touch. T

10、his means that the heat is being transported away from the heat sources and that your amplifier is operating safely. Another advantage of the aluminum chassis is that it is nonmagnetic so acts as a shield against induced hum from the power transformer. Conventional chassis made of steel, which is ma

11、gnetic, are much more prone to this type of difficulty. Conclusion There are many ingredients involved in designing a high quality complete stereo amplifier. However, as this discussion has attempted to show, compromise is not one of them. Instruction for the Model LK-48 48 Watt Complete Stereo Ampl

12、ifier The LK-48 is a complete two-channel stereo ampli- fier consisting of dual 24 watt power amplifiers and dual preamplifiers on a single chassis. It employs the same engineering concept and features that have made H. H. Scott amplifiers the standard in the industry. Con- servatively designed, the

13、 LK-48 will bring you years of listening pleasure. IMPORTANT: Every effort has been made to insure that this kit, when assembled, will perform perfectly. In order to achieve this result, you must read all of the insuuctions and follow them precisely. Let us repeat . READ ALL INSTRUCTIONS CAREFULLY .

14、 FOLLOW THEM EXACTLY, Unpacking your Kit-Pak . Figure l demonstrates the step by step procedure in unpacking your kit, as well as the extremely simple procedures involved in setting it up as a convenient work bench. With the Kit-Pak you can work on any table in the house. When it is time to stop wor

15、king for the evening, all you have to do is close the cover and nun off the soldering iron. Everything is put away in minutes. You arc now ready to begin the construction. After reading these introductory notes, place the instruction booklet into the groove between the cardboard flap and the box cov

16、er. In this way the instructions will be in front of you at all times for easy reference. Check the parts On page 47 of this manual is a descriptive list of the parts included. Before beginning the assembly it is recommended that you check all the parts with this list. It will insure that there are

17、no missing parts, and will help you become familiar with the various items. If you should accidentally damage or misplace any parts, 1. Remove front and rear. Pull off knobs to avoid loss. 2. Carefully remove the rest of the parts and the white platform. 3. Remove brown cardboard pad and bottom cove

18、r. Place small tube package in rear of kit-pak bottom. 4. Your Kit-Pak cover will hold open when you insert special flap through slit in cover. 5. Turn over brown cardboard pad and lift up pad in rear. FIGURE 1 6. Replace white platform. Place chassis in center and instruction booklet behind flap. w

19、rite to the LABORATORY KIT SER VICE DE- PARTMENT at the factory immediately. A four foot length of insulated wire has been sup- plied. It is to be used to replace any missing wir or on.es accidentally damaged. Simply cut off the length required ( a convenient ruler is printed on the inside cover) an

20、d strip off of insulation at each end. Occasionally ve may make minor substitution of parts. Such substitutions are carefully checked and the parts supplied will work as satisfactorily as chose speci- fied in the manual. These changes will be obvious and are mentioned here only to prevent confusion

21、in check- ing the parts list. For example, .005 ,_f. capacitors are used interchangeably with .0047 .f. capacitors. Tools Required A small screwdriver is provided. In addition, you will need a pai1 of long nose pliers, a regular size screw- driver, a pair of wirecutters, and a soldering iron or gun.

22、 A 3 5 watt ( or more) pencil type soldering iron is actually the easiest to use. The iron should be sup- plied with a S!l1aH tip. If a soldering gun is used, it should also have a small tip, and should be used care- fully because of the enormous heat it supplies. Simplified soldering and wiring ins

23、tructions AJl the solder needed to .1ssemble the unit is supplied. If for any reason additional solder is needed, make sure that you obtain 60/40 ROSIN CORE SOLDER. Under no circumtances should you use Acid Core solder. All guarantees are voided if Acid Core solder is used. Heres how to solder joint

24、s correctly (see Fig. 2): 1. Before using the soldering iron or gun, the tip must be tinned for ease of use. First heat up the iron. Then when the tip is hot, wipe with a cloth till bright and shiny, and apply a generous amount of solder. Remove any excess. Repeat this process for all sides of the t

25、ip. 2. Make sure that all leads (wires) and terminals co be soldered are completely clean. Do not use fluxes or paste of any sort. 3. The leads should be mechanically secure before soldering. This does not mean wrapping leads around the contacts sever:il ti.mes. It means a single turn around che con

26、tact which is then pinched tightly with the long nose pliers. If the wire is too large for bending, position the wire so that a good solder connection c,111 still be made. 4. Leads on resistors, capacitors, and similar compo- nents are generally much longer than they need to be to make the indicated

27、 connections. In these cases, the excess leads should be cut off before the part is added to the chassis. In general, the leads should be long enough co reach their termination allowing for a little left over to make a good me- chanical joint. A very handy way of gauging the length of lead to trim o

28、ff is to superimpose the ca- pacitor or resistor right on the pictorial. The pic- torials are all full scale, so by placing the component over its picrnre and allowing about extra on each end for the mechanical joint, yon can shorten the leads quickly and accurately. Sometimes a lead will not seem q

29、uite long enough to reach tbe desired mounting point. In such a case, the terminal lug can be bent slightly to make the connection possible. 5. Place a flat side of the soldering iron tip against the joint co be soldered until it is heated sufficiently to melt the solder. 6. Place the solder against

30、 the heated terminal (with the soldering iron still in contact) and it will im- mediately flow over the joint. Use only enough solder to thoroughly wet the joint. Too much solder FIGURE 2 5 may cause short circuits. The soldering iron does not actually come into contact with the solde1, only with th

31、e joint. It is the heatecl joint that melts the solder. 7. As soon as sufficient solder has flowed, remove the solder tube and then a second later, the iron. Use care not to move the leads until the joint has hard- ened (about 5 seconds). A good solder joint should appear to be bright and shiny. Che

32、ck the joint for rigidity. If it is not firm and tight, reheat the joint and permit the solder already present to flow again. Sometimes a little more solder will have to be added. 8. When soldering certain of the components, such as diodes and resistors, it is advisable to use no more beat than is n

33、ecessary. Excessive heat can damage these components. 9. Keep the soldering iron clean and bright by occa- sionally wiping with a rag. The iron does not have to be cooled for this purpose. If you have never done any soldering before, it wonld be an excellent idea to practice on scraps of wires befor

34、e beginning. Basic electrical assembly procedure Your amplifier kit includes three separate sub-assem- blies: the front (with all the controls and knobs), the main (with all the tube sockets), and the rear (with all the input and output jacks and terminals). You will construct each sub-assembly sepa

35、rately and then com- bine them to make a complete amplifier. The symbol F refers to the front, M to the main, and R to the rear. Each terminal, tube, transformer, etc. has a code number (i.e. Ti, V2, and so forth). Every pin on each of these terminals, or tube sockets is also numbered (i.e. pin 1, p

36、in 2, and so forth). The instructions will call for a wire to be connected to pin 3, V4, for-example. With the instructions will be a pictorial, clearly showing in foll color the connection to be made and its location. With this information you should experience no diffi- culty in making the correct

37、 connection. A series of Part-Charts are provided with all the necessary resistors and capacitors mounted. Each chart applies to a particular page of the electrical assembly instructions. For example -in the instructions that follow you will find a page marked Assembly Group BF-4. The B indicates th

38、at this is part of the electrical assembly. The 1 F indicates that you will be working on the front. The 4 means that this is the fourth page of instruc- tions for electrical assembly of the front. ln the bag of Part-Charts, you will find a Part-Chart BF-4. Take th.is out and keep it next to you whe

39、n working on this page. The first step on the page is called BF4-I and refers to a 2 70K resistor. The first part on the Part-Chart is a 270K 6 resistor. The pictorial on the top of the page will show exactly where this part will go. The part is mounted as directed and the step is checked off as com

40、pleted. The many wires used in the amplifier kit are packed in a small plastic envelope. This envelope contains three separate bundles, clearly marked. For example -As- sembly Group BF-1 involves connecting a group of wires of different colors and lengths. Open the bundle of wires marked front, and

41、spread them out near you. The first step, BFl-1, calls for a 4 yellow wire. From the yellow wires select the ones of the appropriate length and hold them up to the ruler printed on the inside cover of the Kit-Pak. Once you have the correct one, you may proceed as above. IT IS IMPORT ANT TO POSITION

42、THE WIRES OR COMPONENTS IN THE SAME POSITION AS SHOWN IN THE PICTORIAL. If the symbol -(S-) appears in the instructions after any connection, it means that the particular connection with all other wires on the same pin, should be soldered. After the S will appear a number. This number indicates exac

43、tly how many leads or wires are supposed to be connected to the terminal or pin in question. For example: connect an orange wire to pin 2, V6 (S-3). The soldering number (S-3) will always be printed in red, so it can be found quickly. le indicates that there should be 3 wires or leads (including the

44、 orange one) connected to pin 2, V 6, and that all three of them are to be soldered. T his provides an additional check for wirmg errors. Do not solder any connection that is not marked with an (S-). Other connections are yet to be made to this pin before it can be soldered. Frequently one end of a

45、lead or component will be soldered while the other end will not (for the moment). The (S-) will only appear after the description of the end that is to be soldered. After completing the soldering, cross out the (S-) sym- bol with your pencil indicating that it has been done. This is in addition to c

46、hecking off each step. In this way you can glance over the assembly instructions and spot any (S-) that has not been crossed out, indicating that you may have overlooked a joint to be soldered. The instructions which follow have been arranged in a logical order to insure perfect results. Follow them

47、 exactly, checking off each step as completed. For easy reference keep this instruction manual on the inside of the top cover of your KIT-PAK as shown in Fig. I. Types of Wire Provided Regular hook-up wire -These are the standard in- sulated wires chat you will he using most of the time. They ,vill

48、be found in bundles for the different portions of the assembly procedure. Buss wire - T his is a term used to describe short pieces of uninsulated wire. A bundle of buss wire will be found in one of the hardware bags. Mic Lapel - This is a type of cable which has one insulated length and one uninsul

49、ated length of buss wire inside. The cable irsel f has a brightly colored outside insulation. Conductive Vinyl -This is large hollow tubing, usually either black or white in color, which has a hol- low tube of conductive material inside. Between the outer layer of insulation and the inner layer of conduc- tive material is a single strand of uninsulated buss wire. When using this cable, it is important to prevent the inner conductive material from becoming exposed and causing a short circuit. Always keep the outer insula- tion compl