ROWE AMI R-92B Amp 6-09931-02

[TCW]

I just picked up a couple of jukeboxes last night. One is a Rowe AMI R-92B. They said the amp was shot. I had a look and saw fuses blown on the driver boards. F1 of the left and F2 on the right. I'm assuming this is due to faulty transistors. The ones in this are not original. Original are RCA-2N6283 & RCA-2N6286. What is here is NTE251 & NTE252. Should I try to find original spec numbers (RCA-2N6283 & RCA-2N6286) or go with the NTE?

I found the diodes between the transistors are open as well. Anyone have an idea what the spec is on these diodes? Part number 70035009.

Is there a root cause to this failure other than being old and possibly being driven hard for years? Is there something else I should check?

[Ron Rich]

H Tom,
No known reason--age ?? I don't know what the NTE specs are, but suspect they may be better then originals ? As for the "diode"-- what diode, on which board ? Usually Q-5 is bad too, along with out of spec. resistors !! Ron Rich

[TCW]

Ron,

Sorry, the diodes that are between both pairs of transistors.

Tom

[Ron Rich]

Hi Tom,
Are you talking about the items heat sink-ed, and screwed to the heat sink ? Them ain't "diodes" !
Ron Rich

[TCW]

I was misinformed then. There are two, one mounted between each pair of transistors to the heatsink. PH BZV 46 2V0  or maybe its BZV 46 2V0 PH Isn't this some sort of voltage regulating diode?

[Ron Rich]

Hi Tom,
It's a "stabistor"-- or in other words a dual "signal" diode-- later models have a "tri-bistor", and even later models have a "tri-bistor" = one signal diode, in series, mounted on a small PC board in that location --- Ron Rich
Ron

[TCW]

Ron,

Thanks for clearing that up. Si-Stab Silicon stabistor! Any idea as to an off the shelf modern replacement? I also have a model 61024903 amp with that circuit board with three diode type devices on it and two of the three are open assuming they test like a diode. I really need to compile manufacturer part numbers into part data sheets of that period and modern day equivalent.

Tom

[Ron Rich]

Hi Tom,
If you have the devise connected to the whit wires on that board, it is a thirmister. One of the devices is a sig diode and the other is either a stabistor, or a tri-bistor-- markings should be on the board under the components. Generic part numbers are listed in the Service manual/parts sections. Ron Rich

[TCW]

Hi Ron,

I have the parts manual, Section 7 of the ROWE R-92 Phonograph Field Service Manual and Parts Catalog, Page 7-27 and it only has ROWE part numbers, no generics listed for 70035009 Silicon Diode. Do you have something different?

8- 40715103 Heat Sink Assembly (sec figure 7-7, item 18)
l 40710302 Heat Sink
2 21547301 power Transistor Socket
3 21377301 Terminal Strip
4 70035009 Silicon Diode
5 21631901 Diode Retainer
6 21798001 Cover
7 70030206 Transistor (Darlington Amp, RCA-2N6283)
8 70030207 Transistor (Darlington Amp, RCA-2N6286)
9 21318902 Precoated Insulator
10 70075504 Connector Housing
21620702 Amplifier Jumper Plug Assembly
21620711 Amplifier Jumper Plug Assembly

Tom

[Ron Rich]

Hi Tom,
The silly diode is a generic-- such as a 1N914, or equal-- not specific-- Ron Rich

[TCW]

Ron,

Looks like the equal for the 1N914 would be a Fairchild 1N4148. 

I am surprised that when I see people talking about amp repair and replacing the transistors and all the detail that speak into that I have not yet heard anyone mention checking these voltage stabilizing bias diodes. Strange don't you think?

[Ron Rich]

Hi Tom,
I always "check-um"-- and replace that rottin' heat sink compound ---
Ron Rich

[TCW]

It looks like both driver boards need some attention.

Has the 4-07101-03 driver boards. I checked the voltages at the fuses. -36VDC on F1 and +36VDC on F2. Then I check the voltage on R29, it should be around 0.009.

Right Chanel
F1 -36.14VDC
F2 +37.34VDC
R29 -34.88VDC

Left Chanel
F1 -37.2VDC
F2 +37.3VDC
R29 -15.5mVDC

Looks like I will need to come up with some real world part numbers (Not ROWE AMI numbers listed below) for the Diodes and transistors. Help please?

COMPONENT LIST FOR AMPLIFIER BOARD 4-07101-03
C1 CAPACITOR    MONOLITHIC   CERAMIC    .1 Mfd          70020649
C2 CAPACITOR    MONOLITHIC   CERAMIC 220 Pf             70028606
C3 CAPACITOR    ELECTROLYTIC                 47 Mfd 35V    70023012
C4 CAPACITOR    ELECTROLYTIC                2.2 Mfd 58V    70023805
C5 CAPACITOR    MONOLITHIC   CERAMIC    .1 Mfd          70028649
C6 CAPACITOR    ELECTROLYTIC                 15 Mfd 50V    70023009
C7 CAPACITOR    MONOLITHIC   CERAMIC  .01 Pf             70028636
C8 CAPACITOR    MONOLITHIC   CERAMIC 100 Pf             70020601
C9 CAPACITOR    ELECTROLYTIC                22 Mfd 35V     70025810
C10 CAPACITOR  ELECTROLYTIC                22 Mfd 35V     70025810
C11 CAPACITOR  MONOLITHIC   CERAMIC 220 Pf             70028606
C12 CAPACITOR  MONOLITHIC   CERAMIC .01 Pf              70028636
C13 CAPACITOR  ELECTROLYTIC                47 Mfd 35V     70023812
C14 CAPACITOR  MONOLITHIC   CERAMIC 470 Pf             70020612
C15 CAPACITOR  MYLAR                           .10 Mfd           70024002
CRl-CR2 DIODE - SILICON                                              70035002
CR3 DIODE - ZENER 10V                                                70035514
CR4 NOT USED
CR5-CR12 DIODE - SILICON                                           70035005
CR13 NOT USED
CR14-CR15 DIODE - ZENER 5.1V                                    70055527
F1-F2 FUSE - 5 AMP 70072010
P1-P2 WAFER - POLARIZED (4 CKT)                                70075004
P3 WAFER - POLARIZED (5 CKT)                                     70075005
P4 WAFER - NON-POLARIZED (4 CKT)                             70074904
Q1 NOT USED
Q2 NOT USED
Q3 TRANSISTOR DUAL (NPN)  2N2920 60v 0.03A - 78      70030301
Q4-Q6 TRANSISTOR (PNP)      ITT A 56 940                     70030104
Q7-Q9 TRANSISTOR (NPN)      MPS A 0 6                         70030008

[Ron Rich]

Hi Tom,
What part do you need numbers for ?

[TCW]

Thanks for asking but I think I have them all here now.

CRl-CR2 DIODE - SILICON IN4004 (I was surprised by this part number)
CR3 DIODE - ZENER 10V 1N961B Zener Single Diode 10 V 500 mW DO-204AH 5% 2 Pins 200 °C

CR5-CR12 DIODE - SILICON IN4004
CR14-CR15 DIODE - ZENER 5.1V 1N5321B = 1N5231B

Q3 TRANSISTOR DUAL (NPN) 2N2920 60v 0.03A - 78
Q4-Q6 TRANSISTOR (PNP) ITT A56 940 = MPS-A56
Q7-Q9 TRANSISTOR (NPN) MPS-A06

I'll be waiting for parts to arrive before there is any more. I will be going through the same prosses with my CD-100E Amp 61024903. It has the 40710105 driver boards with the Red LED's.