both microdrives start turning at ql power-on

[techy]

Forum ,

Some assistance needed......

Got a project ql of which both microdrives start turning at power-up .

without cartridges loaded.

any ideas , repair tips ,

please let me know .

[Popopo]

Sorry,
I didn't understand what you mean.
Do you want to get both working at once when the QL boot up?
or
Is what is happening to you and you want to solve it?

[RWAP]

I assume when the OP turns on the QL, both microdrives spin up.

I have had this before - but in my case, there was no TV output and the microdrive units run endlessly. That is normally a ZX8302 fault from memory.

It is quite normal for the left hand microdrive to spin up temporarily, but it should stop after a few seconds (this is the boot loader checking for a microdrive in mdv1_ to run the boot file).

Removing and reinserting the socketed chips on the motherboard (8049, ZX8301 and ZX8302) may well clear this issue.

[techy]

@ popopo ,

to clarify ,

as soon as the ql is powered both microdrives start spinning .

and they keep spinning until the ql is switched off.

[Chris_68]

Hi,

Is this without cartridge?

If the advice from RWAP doesn't help it could be the actual MD.
I had this problem with mine and replaced the electrolytic capacitors (with 1uF). To guarantee good connection I soldered a header on the cable. Is the microswitch working as supposed? Less likely this is the problem but better to be sure.

/Chris

[techy]

@ Rich ,


will try those suggestions .

the owner could not tell me if he had the same problem as this ql has been standing several years with white-screen problems .

i repaired the memory so now i can test some more .

[techy]

i have replaced 8049, ZX8301 and ZX8302 for known working ones ....

and the problem remains .

will put the ql on the workbench this evening

any suggestion welcome

[Chris_68]

Hi,

Is this without cartridge?

If the advice from RWAP doesn't help it could be the actual MD.
I had this problem with mine and replaced the electrolytic capacitors (with 1uF). To guarantee good connection I soldered a header on the cable. Is the microswitch working as supposed? Less likely this is the problem but better to be sure.

/Chris

I would start with the connector, 7805, switch, could be ULA and head as well, a coarse test for the head is to measure the DC resistance. A thorough test is described in the service manual

[techy]

@ chris_68 ,

both drives start within a few seconds from each other .

i will swap one for a known good one and see what will happen .

[Chris_68]

Hi,

I can take photos and describe better what I did tomorrow, in service manual section 4 and Fault finding 2.4 indicates it could be TR6 or TR7.

If you have a known working MD then it helps to eliminate anything on the Motherboard itself.
Also make sure you don't have a cartridge inserted.