Minolta X-700: LED and trigger problem, capacitor and IC locations

[Andreas Thaler]

Another broken X-700:

• LEDs in the viewfinder light up when you press the shutter button
• Shutter does not fire when the shutter button is pressed, LEDs go out
• LEDs can then be „tapped“ again
• OFF/ON main switch is not required for this

In post

„Minolta X-700: Electronics fault > spare parts box“

Troubleshooting electronic SLRs: There is little you can do, but do it

I wonder what options there are to find and resolve errors in a highly integrated electronic camera circuit. For example, the Minolta X-700 five ICs, several discrete electronic components and electromechanical parts. Under the hood of the Minolta X-700 It is of course possible to go in...

www.photrio.com

I suspect the built-in electrolytic capacitors (E) and tantalum capacitors (T) are responsible for problems of this kind.

The X-700 has eight of these (numbering according to the service manual):

• C1 (T)
• C2 (T)
• C3 (T)
• C4 (T)
• C5 (T)
• C8 (T)
• C9 (E)
• C10 (E)

Where are the locations of these capacitors?

An abandoned X-700 serves for the section.

(The circuit is no longer 100 percent original as the previous owner and I have already worked on it, but that doesn't matter for this purpose.)

With the top cover removed - top view of the flexible circuit board.

The ring with the contacts for ASA and override adjustment.

Cable connections …

... unsoldered

After loosening two screws on the top, the board can now be bent up (carefully).

IC5, C8 and C9 (latter already removed here) are therefore accessible.

The other positions.

The circuit board around the eyepiece with cable connections and measuring cell.

The board is folded up - IC3 and IC4 become accessible. All connected cables have to be unsoldered before.

The version number of the board.

The oscillating quartz for digital clocking.

C10 in the camera base.


Interim conclusion

• If you are prepared to undertake the extensive task of unsoldering/soldering on the cables, all of the capacitors mentioned are very easy to reach and replace.
• A systematic approach and image documentation of where which cable connects are helpful.
• The service manual also provides information about the connections in a diagram.
• Likewise, all five ICs would be very easily accessible for possible replacement. However, the number of pins (64) and their size pose soldering challenges for ICs 1 to 4.
• Judging by the year the camera was built and the shine of the solder joints, the soldering was done with lead-based solder. It is therefore advisable to also work with such solder in order to avoid any problems when mixing two types of solder (different melting points).

 

[Andreas Thaler]

The logical conclusion to assume that it is a capacitor problem would be to replace all eight pieces.

However, it should be possible to narrow down which capacitors fit into the error pattern and which do not.

The service manual should provide information here.

Things look good in stock so far, although a higher nominal voltage shouldn't be a problem.

But if so, then I want the exact values.


Next Step:

Ordering the electrolytic capacitors.

The cemented eyepiece just obtained through dissection proves to be an excellent magnifying glass.

From now on it complements my other magnifying glass from Minolta


Limitation of capacitors

I looked through the service manual and identified the following capacitors that are likely to be responsible for the problem - LEDs go out when the shutter is pressed, the shutter does not fire:

• C8: 150 uF/3.15 V (Tantalum) - aperture magnet control
• C9: 100 uF/3.15 V (Elko) - mirror magnet control
• C10: 150 uF/3 V (tantalum) or 220 uF/4 V (Elko) - release magnet control

So C8 and C9 in the upper deck under the override and C10 in the camera floor.

With C10 it obviously depends on the version of the board. As far as I know, tantalum was used in the earlier series.

The service manual I have gives the value for C10 as a tantalum version.

To verify this, I checked the tantalum in one of my X-700s.

The printed values on the opposite side of the tantalum capacitor cannot be read.

A little spy helped

The removed small mirror in the optics for reflecting the aperture into the viewfinder (ADR) of my abandoned X-700 placed below the capacitor:

(photo mirrored)

 

[Andreas Thaler]

The shipment has arrived.

A complete set of electrolytic and tantalum capacitors for the X-700 in multiple versions.

The 16 volt version of the 150 uF tantalum capacitor is significantly larger than the original (blue). But things are tight in the upper deck of the X-700.

Hopefully the 100 uF electrolytic capacitor will also fit in, which I only found as a higher-load version.


Unfortunately no success, so for spare parts

I replaced the two capacitors in the upper deck of the X-700 (C8 and C9) and the electrolytic capacitor under the base plate (C10).

• This meant that the LEDs in the viewfinder remained on even after the shutter button was pressed.
• But the camera still didn't fire.
• At least the electromagnet under the mirror box reacted and opened when the shutter was pressed. This can be observed with the base cover removed and the plate with battery compartment removed.
• I tried to trigger the camera using the mechanism in the camera base, but it didn't work.
• The service manual lists various causes for this problem, but none of them seemed plausible to me or would require further dismantling work, which I wanted to avoid.

My guess is that the shutter/mirror is blocked when wound up.

In order to research further, I would have to dismantle the camera and study the shutter and mirror mechanics in detail.

That would be its own, interesting, project, but I don't want to do it in the near future. Hence today „for parts“


But, as always, the work wasn't in vain.

New techniques could be tried out and insights gained.

Here are some pictures with comments - maybe it will help someone with their work

The replacement capacitors, the same capacity as the original ones but with a higher nominal voltage, are larger than those once installed by Minolta.

But the space „under the hood“ is just sufficient.

Here I put both of them into an abandoned X-700 as a test.

The connections are then shortened to fit using side cutters before soldering.

To get to the position of the two capacitors, I unsoldered these cables and loosened the two screws.

My pulling device for fixing the flexible circuit board.

Now you can solder on the board.

The „third hand“ on the left side in action.

The unsoldered capacitors, the end of a service for decades.

The capacity measurement with the multimeter showed no loss of capacity.

But I will also check both of them later with the ESR measuring device.

In order to be able to test the new electrolytic capacitors, and to save myself the final fitting at this point, I temporarily solder them on ...

... and reconnect the circuit board with the associated cables.

Now the X-700 can be activated with the trigger inserted.

In order to be able to look at the mechanics under the plate with the battery chamber, I unsolder it and connect it again with an extension.

A special kind of external power supply

I didn't take any pictures of replacing capacitor C10 in the camera base; the process is documented several times here in the forum and on the web.


Interim conclusion

• Replacing the three capacitors that are responsible for the electromagnets is a bit of work, but can be done.
• If the X-700 does not trip even after replacing the capacitors, a mechanical problem could be the cause.
• In order to make progress here, the mirror and shutter mechanisms would have to be exposed. This also requires some effort with this camera and would be a separate topic/project.

 

[Andreas Thaler]

One last attempt - half a success

Since I couldn't find any further instructions in the Minolta Service Manual for resolving this issue, I consulted C & C Associates' X-700 Electronic Troubleshooting Guide.

And here I found what I was looking for:

The camera now triggered according to instruction 1 in the guide when I connected 2 volts to camera ground via my laboratory power supply and connected a cable on the circuit board (green) to the negative connection of the device.

So it's not a mechanical problem after all!

We continued with instruction 2:

Insert batteries, charge the shutter and set pin 11 of IC5 to ground.

Since this didn't trigger the shutter, we went to instruction 3:

Check connections between capacitor C9 and IC5.

I did this carefully with the magnifying glasses and found that two conductor tracks on C8 were bridging due to too much solder.

I fixed that, but didn't find any other abnormalities.

A test with restored cable connections was negative. No triggering.

So all I could do was try to replace IC5.

I unsoldered the IC from my abandoned X-700.


However, while desoldering in the repair camera, I heated up two pieces of conductor tracks on the circuit board

I was able to patch it, but the IC was no longer sitting flat due to the bridging.

So game over

---

Final conclusion

• Troubleshooting instructions are needed with such highly integrated cameras to have a chance of finding errors deeper in the circuit.
• The manuals from C & C Associates are worth their weight in gold - and just as rare.
• This is where I reached my limits with the soldering iron.
• So I took these experiences as an opportunity to equip myself and practice soldering small electronic components (SMD).
• A project is never in vain, you always learn something new

+++

All information provided without guarantee and use at your own risk.

 

[koraks]

I was able to patch it, but the IC was no longer sitting flat due to the bridging.

Doesn't matter, does it? It takes some painstaking work to bend and patch some more pins, but you can usually get the IC back in place with some effort.

My eye was caught by this patch here:

I assume that this is a patch for a broken/degraded PCB trace? If so, I'd recommend using much thinner wire for this. The problem with thick wire as used here is that the mass of the wire itself and also its size makes it easy to exert excessive mechanical strain on the traces it's attached to. Using thinner wire helps to prevent future repeat damage, and it also helps to glue down the wire to the PCB so it cannot pull on the PCB traces anymore during future work on the camera.

The 16 volt version of the 150 uF tantalum capacitor is significantly larger than the original (blue). But things are tight in the upper deck of the X-700.

This is where SMD capacitors may help. For instance, a Panasonic 16TDC150MYF is a 16V 150uF tantalum cap in a 1210 SMD housing. It will either fit as is, or can be made to fit by carefully soldering two leads to it, depending on the mechanical allowances of the location. Depending on the specific function, you may have some leeway in the capacity or voltage rating, which should bring some more options in view. For instance, it's quite likely that a generic X5R ceramic cap of 220uF/16V in 1206 form factor will work just fine here.

 

[Andreas Thaler]

Doesn't matter, does it? It takes some painstaking work to bend and patch some more pins, but you can usually get the IC back in place with some effort.

When I was working on it last year, I had reached the limit where my previous skills could progress. This IC was difficult to tame because it was small and the connections were short. It was „beyond my resolution limit“.

Then hot air came onto the table for soldering and some exercises followed.

I'm looking forward to the next projects that involve ICs again

 

[koraks]

Then hot air came onto the table for soldering and some exercises followed.

Repairs like these I try to do when nobody else is home and preferably the neighbors are also at work.

 

[Andreas Thaler]

Repairs like these I try to do when nobody else is home and preferably the neighbors are also at work.

I now manage to stop cursing loudly and banging on the table in anger

 

[koraks]

I now manage to stop cursing loudly and banging on the table in anger

Some days are better than others. I do learn.
With great creativity comes great frustration, eh!

 

[Andreas Thaler]

This is where SMD capacitors may help. For instance, a Panasonic 16TDC150MYF is a 16V 150uF tantalum cap in a 1210 SMD housing. It will either fit as is, or can be made to fit by carefully soldering two leads to it, depending on the mechanical allowances of the location. Depending on the specific function, you may have some leeway in the capacity or voltage rating, which should bring some more options in view. For instance, it's quite likely that a generic X5R ceramic cap of 220uF/16V in 1206 form factor will work just fine here.

Thanks, I've now gotten some of the appropriate SMD versions. Only the SMD electrolytic capacitor is no less large than the wired version. But the SMD tantalum version is tiny in comparison.

Searching for and finding suitable electronic components is more strenuous than working with them

 

[koraks]

I find electrolytic SMD caps to be a b*tch to work with on DIY projects, unless they can be soldered onto a newly-made PCB using a hot plate or something. For repairs etc. I don't like them one bit. They're difficult to remove without overheating the part itself and/or its surroundings, and the risk of mechanical damage to pads/traces when removing or repositioning them is very big.

In this case, I'd replace them with X5R ceramic capacitors of an appropriate capacity, which are physically smaller, too.

 

[Andreas Thaler]

Sometimes I think, why am I doing all this to myself? There are so many good films that I haven't seen and literature that has to do with people and not with technology. And I haven't been in the forest for a long time and isn't a camera actually there for taking photos?

Somehow you get weird with hobbies like that