Tektronix Oscilloscope problem

[sido]

Will do so Wm6. I have downloaded the datasheets for the two now. Will look at them tomorrow and use what seems close to the original specs if i cannot find the BFR96.

I am sure i have the BFR96, just cannot remember where?

Talk to you soon.

Cheers Sido

[WM6]

Hi Wm6, i have only found the below transistors on some old UHF Transceiver boards, not the exact replacement, but thought to post for you to have a look and see what you think?

Both the BFR90 and BFW92 are UHF transistors (NPN).

Cheers

You can try with one of those too, check twice for correct pin connection before solder.


BFR90


Type Designator: BFR90
Material of transistor: Si
Polarity: npn
Maximum collector power dissipation (Pc): 180mW
Maximum collector-base voltage (Ucb): 20V
Maximum collector-emitter voltage (Uce): 15V
Maximum emitter-base voltage (Ueb): 2V
Maximum collector current (Ic max): 25mA
Maximum junction temperature (Tj): 150°C
Transition frequency (ft): 3GHz
Collector capacitance (Cc), Pf: 0.8
Forward current transfer ratio (hFE), min/max: 25MIN
Manufacturer of BFR90 transistor: PHILIPS
Package of BFR90 transistor: TO51
Application: Low Power, Switching


BFW92


Type Designator: BFW92
Material of transistor: Si
Polarity: npn
Maximum collector power dissipation (Pc): 130mW
Maximum collector-base voltage (Ucb): 25V
Maximum collector-emitter voltage (Uce): 15V
Maximum emitter-base voltage (Ueb): 2V
Maximum collector current (Ic max): 25mA
Maximum junction temperature (Tj): 125°C
Transition frequency (ft): 700MHz
Collector capacitance (Cc), Pf: 1
Forward current transfer ratio (hFE), min/max: 20/150
Manufacturer of BFW92 transistor: PHILIPS
Package of BFW92 transistor: TO51
Application: UHF, Low Power

[sido]

Forgot to mention, same package type to the original OEM.

Cheers Sido

[sido]

Hi Wm6, i have only found the below transistors on some old UHF Transceiver boards, not the exact replacement, but thought to post for you to have a look and see what you think?

Both the BFR90 and BFW92 are UHF transistors (NPN).

Cheers

[WM6]

Fine, I hope you enjoy your scope soon.

Possible replacement: BFR96, BFR96H, BFR96T, BFR96S, 2n5852, 2SC1803, 2SC1949


LT4403

Bipolar NPN UHF-Microwave Transisitor
TRW, Inc.
V(BR)CBO (V)=30
I(C) Abs.(A) Collector Current=70m
Noise Figure Max. (dB)=1.7
@I(C) (A) (Test Condition)=10m
@V(CE) (V) (Test Condition)=8.0
@Freq. (Hz) (Test Condition)=500M
Semiconductor Material=Silicon
Status=Discontinued
Package=Micro-X
Military=N

BFR96


Type Designator: BFR96
Material of transistor: Si
Polarity: npn
Maximum collector power dissipation (Pc): 500mW
Maximum collector-base voltage (Ucb): 20V
Maximum collector-emitter voltage (Uce): 15V
Maximum emitter-base voltage (Ueb):
Maximum collector current (Ic max): 150mA
Maximum junction temperature (Tj): 175°C
Transition frequency (ft): 5GHz
Collector capacitance (Cc), Pf:
Forward current transfer ratio (hFE), min/max: 30MIN
Manufacturer of BFR96 transistor: PHILIPS
Package of BFR96 transistor: TO51
Application: Small Signal

[sido]

Hi Wm6, I momentarily applied a short circuit to the delay line and the trace did not go center ... actually moved slightly further up on CRT.... therefore the service manual was referring me to the likely cause of fault in the Vertical amplifier section below.

I therefore tested most components so far on the below circuit and have found the Q256 transistor shorting which is starting to look as the problem i am experiencing. Every other component nearby Q256 tested ok.

The part is a LT4403 manufactured by TRW (No longer in Business) and the part has been discontinued.

The only reference to a suitable replacement is a BFR96 as noted below. I cannot even find the datasheet for LT4403 so i can compare pin layout or spec's to BFR96.

I happen to remember i have a few BFR96's from some old UHF radio gear from me radio days, which i will remove and re-fit. I will further test the rest of the components to be 100% certain that the new/used part does not fail again due to other component failure.

Now i got to find where me old radio boards are.

I hope this is me only problem and nothing more with the scope.

Once again Wm6 thankyou for your help.

Cheers Sido

[WM6]

I noticed it says to short the delay lines to see if the beam centers in the middle of the CRT....Does that mean to physically short the delay cable between R338 and R348 on your schematic.

Yes, you need to physically short it for a moment. Use two (instrument) binding cable with clamp on one side and connect it to delay line leads. Look at display and short cable end for a moment. Consult troubleshooting diagram on what you see on display.

Another question....when measuring voltages around this circuit is the deflection output wires supposed to be disconnected from the CRT?? See Pic below.

No, you don't need to disconnect leads to CRT deflection plates. Probably your voltage is according your beam trace deflection position and you can take it as OK for now. Check first marked commutating circuit that integrate both channel together (measure all voltages around it and check visual part status, if possible measure some parts value - electrolyte C at least if exist).

[WM6]

Yes, momentarily only, and look between shortage at display what happen, then consult troubleshooting diagram I posted:

[WM6]

Which circuit block are you referring on my document compared to yours posted below??

Cheers Sid

I think your analogue circuit part is to find here:

[sido]

Which circuit block are you referring on my document compared to yours posted below??

Cheers Sid

[sido]

Hi Wm6, only one response from the Tek forum so far. More useful information here and thanks once again to you.

I noticed it says to short the delay lines to see if the beam centers in the middle of the CRT....Does that mean to physically short the delay cable between R338 and R348 on your schematic.

BTW your schematic is for the 2215 model, same principle, but different component labeling. Not a problem here. Circuit block diagram on your 2215 document is slightly arranged different to my 2215A document. See below. Which circuit block are you referring on my document compared to yours posted below??

Another question....when measuring voltages around this circuit is the deflection output wires supposed to be disconnected from the CRT?? See Pic below.

Note: Very hard to work with this Service Manual unless i print out the necessary pages. A large printer paper format would make my job much easier. Will have to copy documents on to USB stick and take it to a large paper print Company for larger schematics or i might print smaller sections as needed.

Cheers sido

[WM6]

Additional check:

I downloaded 2215 service manual now and found this part of troubleshooting diagram, that suggest this check too: to short momentary delay line leads for check of trace moving:

[WM6]

Yes, it is readable, thanks.

But what you posted is Y deflection amplifier, a part of whole vertical scope circuit (yellow marked on block diagram I posted).

My presumption on faulty working is on red marked part of circuit or something around it:

[sido]

I hope this is readable. I have a on-line scanned copy of the schematic and is hardly readable for me too.

Cheers Sid

[WM6]

Hi Wm6. a bit of update. I got a response from the Tek forum and i am being pointed to the vertical amplifier section also

Here is a quote from a fellow on the Tek forum.....

"Assuming all the low voltage points are within specification then you next suspects are in the vertical output amp section ...starting with Q254-Q257 and working backward. IF any of the low voltage points are out of spec those must be dealt with first"

So there seams to be a problem there wm6

Fine, go along their instructions and please report what you find.

Can you post Y-amplifier part of scope schematic here, in readable resolution, to imagine what we are talking about?